Hmm, a very interesting question, I am assuming that you didn't want to cut ties, but they did, whether for that reason or another that is hidden. He has made his choice, now you must make yours, whether to go in a rage and hate the guy, or still be nice to him, but if he has issues, I would give him space. If say that his dad will beat him if he has other religious friends, it might not be a good idea to bother him too much.
I am deeply sorry that that happens, but there isn't much to be done.
~krill11