baby mama drama

my fiance is arguing with his baby mom about how to divide Christmas. I made the stupid mistake of getting in the middle and making a comment that she will get it her way as holidays always are. He started going off on me after getting off the phone with her to say that he must be getting soft cause people think they can talk to me however they want. I just started to say idk what he's yelling at me for and he slammed on the brakes in the middle of the road and choked me for 5 seconds against the car window saying that he will fucking kill me if I think I can talk to him however he wants.