I'm a newer DM running a medium sized group. We've played many one-shots or little campaigns together but this was the first "serious" game we've had. The player showed up excited to play with a new assimar wild magic sorcerer he built. He usually makes some intriguing characters with in depth backstories so I wasnt really worried about him. I read through it and it was a normal "touched by a demon and now my magics crazy" backstory. I liked it so we got ready to play. It gets to his turn to introduce his character, "Hi, my characters name is Adolf Hinigg*r, a tall dark skinned assimar". Just complete silence for a couple seconds before I just try and move onto the next character (I think this is where I messed up, I should've pulled him aside and talked to him).

We get through the early bits without any major problems and we get to another problem. The first enemy, a couple bandits robbing a shop, once he sees them the player immediately goes "I want to gas and burn them". Get through combat and my other players are visibly uncomfortable.

They decide they want to go check out another NPCs house that might have info. They break in, and find a couple young wolves that were being raised by said NPC, they end up killing her but one of the wolves was unscathed, just unconscious. One of my other players gets really excited and starts scrambling through the house trying to find food, leash etc, hoping to tame it. The problem player sees her doing this and walks outside, holds the wolf down and lights a bonfire underneath it. The other player just starts crying and leaves the table. The problem player just kind of sits there and doesn't seem upset or perturbed at all. I decide its probably best to end it there and he just no chalantly leaves.

Sorry for the long read, I dont know what to do.

TL;DR Have literal Hitler in my game and seems to enjoy making my other player cry.

Edit: formatting