My half-sister's father is being annoying and I'm having the urge to kick him out of my house.
Why would you want to make him leave?
I told them that their father is an asshole and that he badmouths me.
You shouldn't do that to your half sister. Have a talk straight with the father and leave her out of the equation.
What if he denies everything I say.
Even if he denies everything you say you need to still try to communicate with them. Communication will most likely fix the issue that you going there.