I haven't had any real experience with an abusive character myself, but I've played an evil character in the past and it's not at all difficult to not be a horrible person to play with. My character only really cares about himself, it's his survival he's concerned with, and that's why he's sticking with the party, they increase his odds of not dying. It's also why he didn't rush to the aid of the wizard who got brought down by a fire giant and subsequently died (two nat 1 death saves in a row), because doing so would have meant an incredible risk to him. The wizard's player was a bit annoyed, but we talked about it and everything was fine. My character is still kind of an ass, but not to the point of abusiveness, he's just far more likely to make a snarky comment if someone does something a bit silly, or to ponder why we're helping out these people. Despite that, he's also slowly but surely becoming more friendly with the party cleric.

Honestly it takes effort to be an abusive evil character, and you should always remember that it's entirely possible to make an evil character who doesn't sabotage the party, and that people who do make asshat characters and claim that 'they're just playing their character' also deliberately made the choice to make and asshat character, and I think that says something about them as a person. There's some leniency for new players who don't know all the etiquette, but if they're confronted about it and don't stop alarm bells should be going off.