Next time I see my family I'm going to out my dad.
Is he doing something worth getting that much attention?
Yeah, he treats my mom poorly and she won't do anything about it. So I feel like I should.
Wanting to help your mother and father is important but I don't think calling him out in front of your family is the right way to go about it. Outing someone in public has a higher chance of making things worse than better and if it's just your family he's likely to treat her even worse out of spite. Try talking to him privately first and let him know what he's doing.
My dad is an asshole and I should make it clear that it's not okay for him to treat people like crap.
You definitely should make him clear that his behaviour is not right but there is a way to do so. As I said before do it privately not in front of your family.