I think your statement is unnecessarily polarizing. First of all, it depends on the context, and it's not arbitrary. If a new player wanted to create a halfling called Clint Eastwood wearing a cowboy hat, it's not stupid or arbitrary for others to express discontent.
First of all, this isn't likely to come up all that often. Secondly, if it does, it all depends, as you say, on the context. It's up to the DM really, if that's acceptable. I see no reason why D&D
can't support such a character. It's not my preferred style, but hey, whatever works for your game and your group of players.
If a new player wants to create an evil torturer PC, it's not stupid or arbitrary to complain. What's happening is that the other players are feeling threatened by an element that is dissonant with the shared narrative.
That sounds more like a player/DM problem than a problem with the game. FWIW, I think evil characters
should be supported by the rules.
Sure, it's not mature or generous to want to exclude everything you don't like from a system at the expense of others, but it can work the other way around with the tyranny of the minority so to speak. So it really depends on the context, and I'm not sure that your blanket statement and your choice of words are all that helpful.
My choice of words may not be helpful, but I think they're honest.
Again, I ask: why should D&D only support one style of play and atmosphere? That's never been the idea behind it. The very first versions of the games had adventures with robots and spaceships and a sidebar for psionics was in the
Player's Handbook. D&D has always been about running the game you want to run, regardless of whether or not that fits into what other people think is D&D.