I am still expecting, so take what I have to say with that context. IMHO, I don't think that if you ignore this it will not go away. As another person said, it is a cry for attention especially if you have raised him with good values.
Personally, I hated going and doing church activities as a teen and I hated that my parents forced me to do so. However, it was weird because I was in a different school district from most of them. So I pretty much grinned and beared the whole thing because I had to. Furthermore, just because they go to church does not mean much of anything because you can sit there and totally tune just about everything out....I should know. My parents forced me to go to church as they were very, very religous Catholics (Dad had been in the seminary) and his mom was an extreme Catholic.
What about another type of activity that would get him focused with discipline? or something that he would really like to do? Or how about getting a job? If he is too young for jobs, find one through a family friend or perhaps through the church for odd jobs, etc. Short of this, perhaps some therapy to work out why he needs to rebel in this way. Maybe there is something else going on at home that he is not happy with...???? or is he being mistreated/teased at school and this a way to avoid that kind of treatment...to hang out with the "bad boys"???
My parents forbid me to date a guy while I was in college based upon his ethnic background and since I was living away from home. I of course continued to do mostly to spite them because they had threatened to disinherit me, which to me was outrageous. Anyway, had their attitudes been different I would have found out sooner that he was a loser in his own right, not because of his ethnicity and I could have avoided a lot of trouble and almost got myself in real deep. So I would be reluctant to forbid him to hang out with the undesirables, but I would encourage him to pursue new activities that divert his attention away from that crowd.
Really though, I think that trying to find out what is going on and get to the heart of the matter. Coach him...what are his dreams, what does he want to do in life.... ask him how his actions today help bring him closer to achieving those goals? I know teens think that they are invincible and everything seems so far away, but remind him that in 3-4 years he is going to be out on his own and having to live in the real world...not high school.
I don't know if this is helpful or even right, but I guess this is what I would do if I were in your shoes.