Igimar.....a side point.
As far as him believing you are influences by Satan, try to have a lighthearted discussion about it. Ask him "how". How is Satan influencing you. Your mind? Does that mean he thinks you are possesed? Of so then is he whispering in your ear? The bible explains people are free moral agents and have to "invite" the demons into their mind so to speak. Since you haven't done that, what is he saying? Because you don't feel the same way about the religion? Is there a scriptue to suggest that means you are possed by the Devil?
I mean I had these type of stupid arguements with others BEFORE I started questioning the religion of my youth. It just makes no sense, and yet is automatically accepted as possible just because. This whole demon influence thing is fun to poke holes in. When you guys are a little more light hearted, poke a few holes. Get him to laugh. :)