Never heard someone say a new Dwarf PC "won't last long" because there's already a couple of Elves in the party or because the townsfolk don't like them.
I've always found it curious how many DMs enforce rampant NPC bigotry against races not in the PHB-- or not in their preferred PHB-- based on Alignment, but not against the neighboring elves, dwarves, and humans who just murdered their uncles and sheep during the last High Festival.
You know, in the name of realism.
But there’s no reason that people who we’d consider evil can’t be thoughtful and practical and loyal and actually have an agenda that they pursue. Look at other forms of media for examples....Sopranos, The Wire, Boardwalk Empire, Peaky Blinders...these would all be evil campaigns (with maybe some neutral folks in there, too) in a RPG.
I realize it may not be for everyone, but too often this stuff gets dismissed out of hand as potentially disastrous. I find that to be a bit overstated.
Re: evil PCs, I disallow CN and evil alignments unless I know the player well and know it won't be disruptive. More often than not, a player wanting to play an evil or CN PC just is using that as an excuse for their own disruptive behavior. The game is a team sport at my table.
Depends on the setting too; in Eberron there are no "always <alignment>" mortal races and it's not unusual to bump into Orcs or Bugbears or Gnolls whatever (at least in places like Sharn), and so it was nice when we got better stats for playing one as a PC. I had a goblin PC in one of my old homebrews too. The "always evil" thing never set well for me, though. It always felt so reductive and regressive.
On the other hand how do you accord your friend who wants to play a drow or bugbear and walk into town.