How do I go about a friendship with someone who hates religion and God?

I don’t have many friends, I’ve been really lonely lately because my closest friend stopped being friends with me (my ocd symptoms got annoying to her), but I have a friend from high school (I just graduated in June) who I’ve been talking to. He’s not antisemitic, he even considered going to a Megillah reading with me on Purim to learn about Judaism, but he hates religion. He said Judaism’s the only religion that makes a lick of sense, but he could never practice it because the idea of worshipping God makes him sick. He’s always posting anti-religion stuff to his Instagram story though and venting to me about arguments where he loses friends because they get sick of him insulting religion. It’s mostly Christians who get mad at him, he has religious trauma from catholicism so he speaks out against Christianity a lot.

I sympathize with him—I don’t know what happened to him that turned him so strongly against religion, but I understand how horrible religious trauma can be. However, I’ve had to be the messenger when he was fighting with a girl from our school about religion, and I was really uncomfortable taking sides because while he’s my friend, he was being extremely harsh on her for being a Christian, calling her a cultist and insulting her religion horribly. I was going to call him out for a comment that really crossed the line until he started threatening that he was going to kill himself

I’m just not sure how/if this friendship is gonna work out considering I practice conservative Judaism and he’s completely anti-religion. I’m worried this will cause problems and that it’s just a matter of time before he gets mad at me for being religious. I’m also worried that I’m a bad person for not having defended the Christian girl when he said he said terrible things to her. And I wonder if I as a religious person am okay to be friends with someone like this. I really want to be friends with him though, idk how much of that is because of loneliness and how much is because I like him as a person, but he really is a great guy