My father is racist and I'm going to tell him to shut up.
Your father's opinion seems to upset you, how do you feel about letting him know how you feel?
I'm afraid of talking to him
While your dad is horrible for being racist and you should be mad, being aggressive towards him will only make him blow up further. You need to give yourself courage and talk to him about it this issue and let him know you think it's unacceptable if he keeps saying such hurtful things.
What if I start it off with a joke.
You know that racism is wrong and maddening, and while starting off a conversation with a joke can break the ice, a conversation about racist behavior shouldn't be made light of. I think your goal to be calm is better than telling your father to shut up, but I would go into with plans to be direct and assertive.