I think everyone is racist, don't you?
I don't. What makes you think so?
I once had black friends, they were smart and funny guys, but they were very racist.
Just as racism is bad, generalization and stereotypes are bad. Not everyone is going to be racist, and just because you saw a minority being racist doesn't mean all people are. You are being just as harmful as they are.
Are you going to try to change my mind?
I don't need to change your mind to know you shouldn't think everyone's a racist because it's simply not true.