I want to jump in here for a moment and talk about a 3.0 game I ran about6 or 7 years ago.
One member of the party was from a Magocracy where he was a guardsmen, (Malita) and had spent almost 5 years tracking a serial killer who raped and killed both men and women. His background was twisted and dark. He wrote it this way (with my approval) becuse he was playing a Paliden and wanted a 'nemisiss' that was as dark and vile as he was light and exulted.
We had another party member who was from a small psionic heavy city state. His background included inhuman experaments with makeing intelagent items by psi like power ripping peoples mind out and attaching them to items as a type of slavery. He was appaled at his people and had long since ran away.
Every player new there were some 'dark' parts of my world, and this was a excepted part of it, but most didn't know the enitre of these two stories.
The PCs found out about the city state, and found that they made a psycioactive skin that had 7 diffrent demmons/devils dound to it. Almost everyone right away realized it was a bad Carnige rip off. But it got away.
it was 2 or 3 games later they found a guy who's mind was messed up and he was catatonic, in the woods. I expected this to side track them to a local town, but they decided to instead leave the NPC with him ( a 3rd player character's 15 year old daughter) and continue to the ruins then come back for the two of them.
Now the catch being that catatonic man was the serial killer wearing this new suit. It was 'bonding'. I thought he would wake up in town and there would be a whole show down thing. But the Pcs left him for 3 days with this girl. To make things worse we had a paliden that would use "Detect Evil" at the drop of a hat, but who did not do so here.
The PCs came back and I said "Look instead of discribing what is here we are going to flash forward 25 mins, and tell you what you figured out." then I explained who the guy was what he was wearing, and that he was a X level rouge with that artifact on, that he raped and killed the dauhgter in a gruesom way, and that he had fled but they could track him.
I had though the PC who just lost his (in game) daughter would be upset, but yet another PC (One who has a real life daughter of simalar age) was more outraged, and walked out. He said dark was one thing, but this was too far, he would come back for our next campiagn, but he was out for this.
No one called him a premadonay. No one even said anything about it, if he can't hanndel that sort of thing then we will just adjust for the next time.
How ever 1 PC in that game was a half dragon Fighter. (Infact that would be the PC who's daughter died) Had someone had the same reaction to me allowing the race then it would be diffrent.
I can understand somethings push the wrong buttons, I really can, but to say "I can't play in a game with dragonborn" and then to defend that with "Well you don't want to play in a game with a rapest" is just beyond crazy...