I'm not going to invite a friend of a friend to a party
Why don't you want to invite this person to a party?
He is a bad guy. He called me a nerd freak and I think he came over to my house once to get information from me.
You're justified to invite or not invite who you want to your party, but be sure your friend knows why you're excluding their friend. Try not to damage your relationship with them over something someone else said or did.
Thanks. I'll be sure to let my friend know.
That's a good idea. It's important to be honest with your friends, especially when it comes to people they hang out with a lot.