“Get Out!”
Just kidding of course.

I have that fear every day. I have two step sons that have been with me since they were babies, and their bio father is religious. So alternate views are inevitable in my house.
I have always told them, I will love you no matter what, but don’t expect me not to challenge you with whatever you believe. Even if it’s the same as I believe.
I tell them it’s more important to know HOW to think, rather than WHAT to think.
But that’s tough to watch. I know some don’t feel as strong as I do about it, but to me it’s almost the equivalent of watching a loved one struggle with drug addiction.
Good luck to you sir.

I would tell him that there are these "special summer camps" that will fix him..

I would ask why? And move on.