I'm thinking of not speaking with my step-family and it angers my mother a lot
Are you also angry with your mom, such that you are not speaking with her?
I'm just pissed off at them all.
It's always good to have good relationship with people. Even if they're your step family, you should at least be nice to them.
They make me pissed so fuck them.
I don't know what it is that they are doing to make you mad, but I'll accept that you don't have to always like them, especially the step-members of your family.  However, they are your family, and your refusal to talk to them is just causing undue strain.  They probably don't mean to offend you, so you should just be civil and polite with them.