In "The Pharaoh," the professor is right to point out Don't Touch It, You Idiot! about the Staff of Anubis because ancient artifacts are delicate and can easily become damaged.
Marinette's arguments in her own defense in "Rogercop" are far more coherent than the narrative wants the viewer to believe:
After being accused by Chloé of stealing her bracelet on the flimsy grounds that she tripped near Chloé's purse earlier, Marinette points out how there's also weak evidence tying some of her classmates to the apparent theft (Sabrina was the last person seen actually holding bracelet and Nathaniel sketched a picture of it). Though it's meant to be seen as Marinette trying to scapegoat her classmates to shift the blame off herself, that wasn't what she was doing. Rather, Marinette was pointing out that in the absence of solid evidence, she's no more guilty than anyone else and thus doesn't deserve to be singled out. She even admits that she is a suspect and agrees to let her bag be searched if everyone else is subject to the same treatment. It gets particularly egregious when her invoking Everyone Is a Suspect and stating that the thief must be someone in the room is treated as her accusing her entire class of stealing. While it can be argued that she could've gotten her point across less harshly and that it would be a huge breach of privacy to have the entire class's bags searched, her insisting that she be treated the same as all her classmates isn't an unreasonable demand. Marinette's only real fault in the situation was trying to make an exception for Adrien due to her crush on him.
After Nino plays the video he recorded on his phone, Marinette points out that Sabrina was filmed holding Chloé's bracelet before it disappeared and then suggests that Chloé search Sabrina's bag. This is portrayed as Marinette making an unjustified kneejerk accusation at Sabrina. However, that's not what Marinette was trying to do, something that she even states. Instead, she was drawing attention to Chloé's Double Standard in ordering only Marinette's bag be searched but not Sabrina's when both of them had evidence connecting them to the missing bracelet. She might've been able to get her point across in a gentler manner, but her observation was still valid.
Tom Dupain is supposed to be a Reasonable Authority Figure when he tells Marinette to stand down and let the adults handle things. However, Marinette correctly points out that she has every right to speak up and defend herself when she's being wrongly and baselessly accused of theft. Not only that, but one can hardly blame Marinette for taking matters into her own hands rather than relying on adults, given they've failed to rein in Chloé for years. In fact, just earlier in the episode, Roger got fired by the mayor for refusing to conduct an illegal search to satisfy Chloé's whims, and none of the adults said a thing about it.
In "Darkblade," Armand D'Argencourt's seeming Sore Loser tendencies after losing the mayoral election. Given his humiliating defeat at the hands of his Jerkass opponent, (Chloé's father, of course) said defeat being a textbook Ironic Echo of his opponent's ancestors doing something similar to Armand's family long ago, and the public constantly hounding Armand for said loss, you really can't blame him for being so frustrated—and are probably surprised that he does nothing worse than Poke the Poodle (at least before Hawk Moth turns him into Darkblade) during his Rage Breaking Point.
A couple examples concerning Marinette and her supposed "selfishness" in "The Gamer":
Marinette expresses last minute interest in the school's video game tournament tryouts due to the prospect of spending time with Adrien. Alya calls her out on this, saying that representing the school in the tournament is Serious Business and that she shouldn't enter just to flirt with her crush. However, seeing as the contest was open to the whole school, Marinette had as much of a right as any student to enter, regardless of how much she may have cared for the actual tournament. Moreover, only the students with the two highest scores would move on to compete in the actual tournament, so Marinette wouldn't even be partnered with Adrien unless she actually proved she was good at gaming by scoring high enough to get at least second place behind him.
Marinette quickly proves all her doubters wrong by getting the highest score out of everyone who tried out… and is still portrayed as being in the wrong for entering the tournament, this time for only thinking about herself and being inconsiderate of Max's feelings when the tournament meant so much more to him and he had trained for an entire year to compete. The ending even drives this point home by framing Marinette dropping out so Max can take her place as the right thing. The problem is that the whole point of organizing tryouts, as well as the video game tournament in general, was to have students compete against each other to determine who's the best and that winners of competitions are generally chosen based on who earns it rather than who wants it the most. It's hard to fault Marinette for doing exactly what the school and the tournament expected of all participants, especially when Adrien, who also beat out Max for a spot in the tournament, isn't depicted as also being selfish.
Ladybug not taking Chloé's advice in "Antibug." As she points out to Cat Noir, Chloé had lied to them earlier about her fight with Sabrina and was otherwise useless in battle as The Millstone and a bystander. She had no reason to trust Chloé's word.
Marinette in "Guitar Villain" when producer Mr. Ross wants her to design Jagged Stone's album cover to mimic that of XY's. Although Tikki tells her to stick to her guns and design it the way she would, Marinette has a good point in saying that Mr. Ross told her to design it a certain way: most graphic designers have to compromise their styles to satisfy clients. Marinette was just really lucky that Jagged had enough power as a musician to override what Mr. Ross wanted and tells Marinette to design it in her style.
Throughout "Riposte," it's highlighted that Marinette is unfamiliar with all the intricacies of fencing. However, a few times, she seems to have more sensible views related to the sport than the more experienced fencers:
When Kagami suggests that she and Adrien be disconnected from the scoring machines for more freedom, Marinette asks how they're supposed to tell who touched first without the machines. One of the members of the fencing team tells her they'll just have to watch the bout closely, and nobody else seems to protest. However, Marinette is right to be concerned: though electronic scoring machines are not without shortcomings and criticism, they were still introduced to fencing to prevent human errors and biases and are generally considered much more accurate that human eyes. D'Argencourt was twice unable to declare a winner because it was simply too close to call, so disconnecting Adrien and Kagami from the machines would likely only make things even more difficult. Not only that, but one of the fencers is a student of the referee's fencing school, and the episode also implies that D'Argencourt is biased against Kagami: Marinette later says she wasn't sure who touched first and only that she thought it was Adrien, but D'Argencourt treats it like proof Adrien won. When Adrien later argues that he thinks his opponent struck first, D'Argencourt dismisses it for no reason other than, "The referee has the last word."
At one point, Kagami pushes Adrien off the mat and into a pole, after which they continue their bout up the stairs and throughout the school. Marinette questions if this is really what fencing is all about, to which D'Argencourt insists it is. Anyone with a basic knowledge of fencing rules, though, would disagree: jostling your opponent is known as a corps-a-corps and will get you penalized while retreating off your end of the fencing strip ends the bout with the point going to your opponent. These and various other violations that Adrien and Kagami commit during their bout (turning their back to the opponent, being too aggressive, etc) could easily get them both penalized, disqualified, and perhaps even banned in an actual tournament.
The show portrays Marinette's opinion that Adrien won in this final bout against Kagami as incorrect; Adrien thinks Kagami struck first and later outright says Marinette made a bad call. However, a Freeze-Frame Bonus seems to show that Adrien really did touch first. Additionally, Marinette is likely also correct for a different reason: Adrien explained earlier in the episode that in the sabre fencing that the team practices, priority matters more than who strikes first when determining who gets the point. Adrien more arguably had priority due to lunging forward as he was attacking while Kagami moved her arm back as she was turning her back to him (though this would be an illegal move in Real Life, anyway) for her final strike.
When making her peace offering to Marinette in "Chameleon," Lila states that all their classmates are idiots. Considering how easily she manipulates them and some of the lies she gets away with, she may have a point. She also stated earlier that they ought to be friends instead of enemies because nothing good or productive would come from her and Marinette fighting over a boy, and given what happens when Marinette and Lila do officially become enemies, it's hard to see this as a lie when the sentiment seems so true.
Marinette in "Chameleon" decides to expose Lila as a liar since Lila makes a mistake in keeping her lies consistent. Adrien is portrayed as being in the right when he discourages Marinette from making a confrontation to avoid making things worse, but plenty of fans have pointed out that doing nothing against Lila goes against the lesson of the Origins Episode that "Evil only triumphs when good men do nothing." Additionally, doing nothing does not fix the problem, given Lila has made it clear to Adrien and Ladybug by continuing to lie after being politely discouraged that she will not reform, so there is nothing positive to be gained from this option even if the alternative is bad. In fairness, Adrien finally admits in the Season 5 episode "Revelation" that the advice he gave to Marinette was bad and only allowed Lila to cause even more trouble.
It was revealed in "Catalyst" that Marinette's attempts to expose Lila's lying have so far been brushed off by her friends, who think she's jealous of Lila for having feelings towards Adrien. It's not hard to see why they think this as Marinette's crush on Adrien often causes her to make poor decisions in scenarios relating to him (including her first confrontation with Lila), not to mention many of her antics have fallen into unhealthy stalker territory.
Chloé shutting down André Glacier's ice cream stand in "Revolution" is presented as yet another example of her pettiness and cruelty, but it's undermined by the fact that she actually has a justified reason to shut it down (it's operating without a permit, which is illegal in Real Life, and the only excuse André gives for not having one is, "I don't need one").
