I have been friends with Jews, pagans, Buddishts, and even a shinto couple in my life. I do not have a problem with their faiths as long as they don't put down my strong Christian faith.
I am a Wiccan Witch and my husband of like 30+ years is a Catholic. So a Christian who is friends with a Satanist is fine too. There should be more friendships like that and there would probably be a lot less hate in the world.