As mentioned before, we can openly talk about stuff like flaying elves to death with minecarts shooting goblets, and we can create creative ways to murder nobles "because they mandated the kids get toys". I can kind of see how people saying they'd openly murder trans/intersex dwarves in game would warrant moderation, but it's ALMOST a double standard, especially considering it's a game.
I have to say, as development has progressed and the characters in the game react a little more realistically to death and violence, I personally can't take as much joy in the slaughter as I used to. Even when wiping out murderous bandits, it makes me feel bad when I decapitate one of them and his buddies all start shouting, "My friend Urist Hellvillain the Eater of Children is dead, I can't believe it!
" If I recall correctly even Toady mentioned feeling bad about his own work during playtesting a couple years ago, when he'd toss someone's severed head into their family's house and all their friends and relatives started weeping and expressing their grief. I think, as you said, most violence in video games (or any other medium) is just cartoonish slapstick stuff that no one should take seriously. The violence against elves and nobles is great because it's over the top and because the targets obviously richly deserve it--the elves have no room to complain about having their bodies reduced to gristle in some player's overcomplicated deranged death machine because they're arrogant freaks who murder people over trees, similarly people enjoy exterminating nobles not because they issue mandates but because they try to use the dwarven justice system (which of course they themselves are immune to) to have innocent people jailed or killed when they don't get their way. There isn't a similar joyous vendetta against humans in DF, for example, because humans generally don't do bad things unless they're provoked. Other stuff like the mass butchering of cats and murdering useless migrants and such is a reaction to flaws in the game engine itself--it makes it difficult just to keep the game running when you have dozens of cats and gormless Soap Makers running around underfoot, but it's only a problem because it devastates your FPS and you couldn't just send them away or deal with it in any realistic fashion. It's such an unrealistic situation that you can't take it seriously.
Players openly daydreaming about murdering imaginary people just because of their own perverse obsessions and hatreds is different. It isn't real and it isn't harmful to anyone, though it obviously can make the community seem unwelcoming and such, but it does come from a very different place than someone drowning nobles because they cause problems in the video game, and I think that's worth acknowledging.
As far as comparing Bay12 and Steam goes, I'm sure it makes a difference that there is a barrier to entry here--you have to wait to get an account, and I would imagine a lot of people who just want to vent about something cool off while they wait and forget about it. If anything, I think Toady should make it more difficult to join this forum--perhaps only people who pledge on Patreon could be allowed in, for example, or he could spend some of the money from the game's budget to hire goblin cosplayers to besiege your house in real life and only those who survive may have an account. I'm confident that the Steam forum, on the other hand, will be like every Steam forum: some people slavishly inventing weird new praise for the game (like a Darkest Dungeon thread I saw once that said the game was brilliant because it implicitly taught players to use corporate stress management techniques, which it does not), some people spending all their time posting about how much they hate the game, some people posting about how much they hate people who post about the game, and the rest just asking random questions that vary from reasonable (how do I make the dwarfs fight the bad elfs?) to bizarre (I accidentally marry horse while playing Dwarf Fortress, please advice).
Anyway, censorship is always unambiguously good and free speech is always unambiguously bad. Anyone who disagrees should be punished for expressing their incorrect opinions. That's the way I live my life, and that's how every internet forum should be run. It's the best way to avoid controversy. In my experience, the people who whine the loudest about their free speech and about the mods being mean to them are the people who absolutely should have their voice and ability to participate in community taken away.