In the same way, some fans loved it for its thematic departure from the previous installments, while other fans hated it for exactly the same reason.
And similarly, there was a lot of nasty feuding between fans of this film and those franchise fans who preferred the canonically-incompatible Terminator: The Sarah Connor Chronicles, because of the two works' very different styles and/or feelings of "Sarah Connor is the franchise protagonist and if you don't accept that you must have problems with women".
Faux Symbolism: Marcus is deliberately tied up in a cruficified position while receiving his lethal injection in the film's opening foreshadowing him as a sacrificial savior by the story's conclusion.
The leaked alternate ending becomes this in spades in the wake of the massive plot twist of Terminator Genisys.
Internet Backdraft: The fan outcry over the leaked ending of T4 prompted the studio to completely change the movie's third act. It was originally going to have John Connor die, with the Resistance putting his skin on Marcus's frame so that humanity wouldn't lose hope due to the loss of him.
Moral Event Horizon: General Ashdown cements himself as an immovable object when he relieves John Connor of his command after the latter insists on saving Kyle Reese. To be fair, Connor knew that Reese was his father, and he didn't want to break it to Ashdown for fear of being totally disbelieved (given that Reese is actually younger than Connor and became his father thanks to a temporal paradox), but Ashdown, 404 as he may be, reacted rather callously to Connor's persistence. He even goes so far as to do it in front of his subordinates! To drive the point home, said subordinates stick with Connor anyway in solidarity, because they somehow have a hunch that Connor's further in the right than Ashdown.
Uncanny Valley: The T-800 at the end has a digital rendering of young Arnold Schwarzenegger's head. Justified, because the real Arnold has aged noticeably since 1984 just like everyone else, and the CG effect is actually pretty appropriate for a robot.
What an Idiot: Resistance HQ broadcasting the shutdown signal from its own location, rather than a buoy or an airplane.
WTH, Casting Agency?: A rare instance for Christian Bale, who was widely seen as miscast in the role of John Connor.