The action is perceived as extreme, but in the circumstances it was accepted. Jet's slapping of Amber was because she was deliberately rubbing salt in the wound of a very recent and painful event, but most fans tend to "forget" the fact that she was deliberately goading him on.
Jet gets called on the slap at the drop of a hat, no matter how irrelevant the situation.
Princess Amber becomes a Yaoi Fangirl and Jet decides to pull a Face-Heel Turn. She decides to give up her love of yaoi and Jet pulls a Heel-Face Turn. The fans never live the second of either side down and still portray Princess Amber as a Yaoi Fangirl and Jet as a villain.
The Story's lesson is that while one should forgive minor offenses but if you have committed a major offense then the fact that you have only done it once is flat out irrelevant.
Zig Zagged: The story is a case of Flip Flop of God on whether if Jet actually deserves his reputation or not.
Averted: Fans raise their eyebrows at Jet, but they let it drop after a while.
Enforced: After seeing how the fans responded to an event, the writers focus on it more and more.
Lampshaded: "I make one mistake, and you guys condemn me to life as a monster. Some friends you are!"
Exploited: Evulz takes advantage of Jet's new bad reputation to spread dissent among the heroes.
Defied: The very next episode Amber gives Hiro a reason to slap her as well, right in view of Sapphire who approves. What was starting in the fans but had not yet become the trope died down at once.
After seeing how the fans reacted to it, the writers address the situation by having his friends confront him; Jet argues successfully that it isn't fair for them to judge him based on one moment of weakness, and they reconcile, putting the incident behind them.
Reconstructed: Despite this, Fan Dumb pans the episode as a thinly-veiled Take That and clings to their image of Jet the horrible abusive Jerkass.
Played For Laughs: The writers catch on to it and turn mentioning it into a running gag. Jet is know known as "Princess Beater".
Played For Drama: Jet's True Companions find out that he struck Amber and are horrified, unsure how to treat him now that he's "revealed his violent side". Jet finds himself pushed to the outskirts of the team thanks to his momentary lapse, and is rather miffed that they're letting one action override all the good he's done.
Yeah, I know I created a really lousing "Playing With Wiki" once, but I've gotten better! Can't we just forget about it?!