I've never liked Ron, though I don't agree with all the character bashing he gets. Well, if I want to be more accurate, I don't agree with character bashing at all, but thats neither here nor there. I try to avoid fics where he is the main character since he's one of my least favorite characters. For me personally, I feel that Ron lessened Harry's potential. While it's true he gave him a good friend, and one that stood by him for the most part, but Ron was pretty dang lazy at Hogwart's and he dragged Harry down with him. I think even some small part of him was attracted to Harry because of his noteriety as 'The Boy Who Lived'. I think that if Harry had not had Ron as such a deep and close friend, he would have been a much better student. That's my reasons for disliking him. I don't want to debate, just stating my reason and it could be the reason of others.
Female character bashing is horrible in slash fiction, especially if those characters are paired canonly with the author's fav male character. It really breaks my heart, but it occurs far to often. Just like Ron, I'm not a fan of Ginny as far as the books/movies, but in fiction as long as she's not the main character, I tolerate her presence, but hate when she is made out to be completely unlikeable.
I think a lot of fanfiction authors forget that the characters are already flawed and feel the need to add their own flaws, character bashing aside. Adding flaws to already flawed characters only exacerbates the flaws and makes them turn out terrible and seem overly OOC. And others, they just hate on them. Character bashing is really pointless and ruins perfectly good stories. I've exited out of more stories than I care to count because the bashing got to be too much that it seemed the focus of the story was to bash the characters. I have a lot more respect for authors that don't bash than those that do.