You are right that they are no longer a friend, but that’s because they were brainwashed into thinking their friends perfectly normal identity is a result of Satan controlling them, or whatever. Christianity, and most other religions, cause more harm than good in our modern times.

We have outgrown religion’s usefulness as a species, but people are so afraid of death, and the meaningless of life, that they will deny reality to hold on to the hope of a better life after this one.