Come to think of it, just find/replace for your fandom of choice here.
Dear Ace Attorney fans,
I know that characters in the Ace Attorney games do frequently turn out to be more (or less) than what they first appear to be.
I know that the series' writers do sometimes throw in plot twists that blow everything we thought we knew about the cases, characters, and overall plot out of the water.
I know that those same writers have a tendency to give at least vaguely sympathetic motives and/or backstories to most of the villains of the series. So yes, a few of them can actually come across as Just Misunderstood in some way or another.
I even know that there are quite a few characters whose positions on the Wheel of Morality are a bit more sketchy than Capcom would have us believe, whether they're supposed to be good characters or bad. Why hello there, famous Apollo Justice fandom example.
But guys? I think it's safe to say right now that, until proven otherwise, Kristoph Gavin is a pretty fucking evil jerk. So it's probably alright for people to write him as a villain without having to work particularly hard to defend themselves against your righteous fury.
It's true that we don't know everything about the character, and that the Apollo Justice arc is still going at the time of this writing. But we do know that he murdered people (one of them would have been a little girl, had things gone Just As Planned), and messed up the lives of several others, essentially because he got fired by one lousy client (but incurred no other penalties or lasting damage to his professional reputation that we know of). At the very least, we can agree that he's none too sane.
To be fair, you guys have every right to write Kristoph as a poor, misunderstood woobie as much as the hell you want, but everyone else has the same right to ask you what crack you're smoking when you complain about how people could be so mean to a character who is (as far as we know) one of the least remorseful and most batshit of the series' villains in their fanfics.
And if all else fails, can't you just stop worrying and learn to love the "AU" tag?