It's occurred to be before that the controversy around the character of Hank Pym (a.k.a. Ant-Man/Giant-Man/Goliath/Yellowjacket/Wasp) has a mental illness component that's rarely addressed. The character has polarized Marvel readers since that 1981 issue where he struck his then-wife Janet Van Dyne (a.k.a. the Wasp)*. That issue, and the larger storyline to which it's connected, has been out of print for years, so the actual context of the event has been largely divorced from that one panel of Hank hitting Jan. But since the whole story has finally been reprinted in the Avengers: Trial of Yellowjacket trade paperback release (which I strongly recommend), there's finally the opportunity to examine Hank's deeds with closer scrutiny.
On the one hand, Hank does behave badly, and he's not so far gone that he loses responsibility for his actions. Having just re-joined the Avengers after an unsuccessful return to his scientific work (during which Jan tayed on the team), Hank's an unstable nervous wreck, and he takes his frustrations out on Jan. Jan, trying to be the good wife, tries gently reasoning with him, even though he's snapping at her over every perceived slight. What's important to note is that while the physical abuse of Jan is often brought up, the verbal and psychological abuse is downplayed, but that played just as much of a role in their divorce. At one point, when Jan's trying to decide which of her Wasp costumes she should wear to the Avengers meeting, Hank uses his Yellowjacket suit to blast one out of her hand. He's using a deadly weapon to destroy her property, and thus issuing an implicit threat. Jan doesn't say anything in response, still under the impression that she can help him (and thus continuing to enable his use of her as a scapegoat, as is so often and sadly the case).
Hank's behavior is reprehensible, and it goes beyond a domestic dispute and into nearly manslaughtering the entire Avengers. He creates a robot to attack the Avengers so he can shut it down and appear to have saved the day, but like all robots in these stories (most notably, Hank's accidental creation of Avengers arch-nemesis Ultron), it goes berserk, everyone sees through Hank's ruse, and Jan ends up shutting it down. It would be kind of hard for him to plead insanity when he had enough rational ability to make a giant killer robot, even if it ultimately couldn't be controlled. Looking closely at Hank's behavior, he's aware that he's doing the wrong things, but he ends up doing them anyway because he can't control his impulses and is so desperate to prove his worth. He doesn't try to win back the Avengers or his wife after these events, realizing the immensity what he's done; he doesn't even accept any charity, despite the fact that he was living off of Jan's trust fund and is otherwise penniless.
So yes, Hank is responsible for his sins. But while he could have controlled himself even in the context of his nervous breakdown, the event did not occur in a vacuum. Hank had previously been unstable, due to his own low self-esteem, his unhealthy relationship with Jan (a younger woman who he had nothing in common with, other than her resemblance to his dead first wife), his guilt over the creation of Ultron**, and the adverse psychological side-effects of his powers. And during this whole time, the Avengers were right there, watching but doing virtually nothing. Nobody on the team asked Hank what was bothering him. Nobody suggested therapy for him or Jan, together or separately. Nobody was worrying about his long-term mental stability, even when he fell into delusions where he thought he was another, more aggressive man. His marriage to Jan occurred when he was high on Science Chemical Fumes and called himself Yellowjacket, believing himself the murderer of the original Hank Pym. The great fraternity of superheroes was nothing more than a Greek Chorus bearing passive witness to the downward spiral of one of their founding members, up until his baggage became a physical threat.***
It's worth noting that this story happened right before the similar downward spiral of another Avengers founder; Tony Stark, a.k.a. Iron Man. At this point, most of the Avengers didn't know Tony's secret identity, and when he ended up dating Jan shortly after her divorce, she wasn't aware that she was dating one of her (and Hank's) co-workers. Tony fell for her and couldn't bring himself to tell her the truth, at least until Captain America guilt-tripped him into doing so. The result was a messy break-up that fuelled Tony's own depression, until he outright disappeared from the Avengers. This was due to the story in his own book, where the psychological warfare of Obadiah Stane caused him to sink into an alcoholic relapse. Tony's storyline was controlled by the Iron Man creative team, but you could see Tony fraying at the edges bit by bit in the Avengers, withdrawing from interacting with the team (and his ex), with nobody doing much to check in with him.
The Avengers have an absolutely abysmal track record taking care of their own. Hank is only one of the heroes to have a catastrophic nervous breakdown while on the team; the list of fallen heroes on the Avengers roster include the aforementioned Tony, Wanda Maximoff, Pietro Maximoff, Simon Williams, Clint Barton, Bruce Banner, Carol Danvers, and more. But as far as he fell, Hank managed to pick himself up. He earned Jan's forgiveness (and even a few reconciliations, however temporary), he earned his place back in the Avengers, and everything he's done since has been an act of atonement. He's not entirely stable, but nobody is immune to stress, especially not as a superhero.
Can't he get fandom's forgiveness?
*(It's worth noting that the writer of the original story, Jim Shooter, wrote the scene as Hank pushing her away with more force than intended, but the artist drew it like just another superhero fight scene; hence, an isolated incident became a scarlet letter.)
**(Who's actually killed millions of people. How come Hank gets more grief for one slap than for creating a genocidal anti-organic monster? )
***(Joe Casey's excellent Earth's Mightiest Heroes mini-series portrayed the wedding in a much darker light, where Jan and everyone else was playing along with Hank's delusion to avoid an even greater meltdown. Not sure if this makes the Avengers look better, or much, much worse.)