Yes, by putting those signs there, he's encouraging them. They're determined to convert him. They'll break him down with love, dammit! Christian proselytizers are the type of people who believe you don't have anything in your life and so you need Jesus. All you have to do is read their testimonies: "Once I was miserable with no direction in life and then I found God!" They think the most hostile people are that way and so will keep preaching to them until they give in.

What they don't count on is that you reject their religion not because you haven't studied it but because you have. So hit back in that area--they leave it totally unprotected. A few well aimed jabs there and they're gone. But, of course, it means that DO have to study it with a critical eye.