I'm not saying PCs can't or won't commit evil acts no matter their stated alignments. It's just been my experience that PCs with an actual evil alignment written on their character sheet are disruptive to group play.
It's kinda like "my PC is evil, so I get to play an asshole".
No, you don't get that "privilege". Least not when I'm running a game.
RPGs are a group experience, and if that experience is to be successful, we all need to be on the same page.
Besides, aren't PCs supposed to be heroes of some sort, even if they might be at the "Dirty Harry" end of the spectrum?
Maybe I'm off target. Maybe "evil" is a legitimate alignment in campaign play. Maybe they can work with good aligned characters.
Am I wrong?