Why dose he swear the way he dose?

I have a step dad and he seems to swear at me a lot and everytime he dose I flip because I no my real dad and he would not like me to get sowrn at.
my step dad has a go at me if my room is a mess but he leave all his stuff laying around the house I hate him!!!!
my mum takes my side in this but still he dose not change he even swears at a 4 year old (his son) me and my older brother see what he is doing he cant handle his son or anything so he take it out on me and luke and callum all of us e even takes it out on my mum.
please help me what should I do?

sounds like a real jerk. tell your mom you can't deal with him anymore and keep remimding her that he's not your dad and that your dad will never treat you that way.