Uh, talking about porn at all, and to this extent, tells me this guy is socially inept and frankly people who talk about sexual topics so outright usually are looking for people who don't have boundaries (people who would call them out) to latch onto because 99% of people will avoid them once they see they're unstable. Your other friends have self respect and cut this creep out of their lives.

YOU deserve to not feel uncomfortable and should tell him you think it's inappropriate and you won't talk to him about it anymore or want to hear it. YOU DONT HAVE TO FEEL UNCOMFORTABLE and him being a guy does NOT make this ok! He sounds disgusting tbh. There's a reason other people have been driven away and it's not your job to still be there just because he's lonely.

You don't owe him friendship, it doesn't make you a good person to let him use you as his social crutch. I say this from experience hanging out with the bottom feeders of society because I wanted to be the "cool girl" who didn't shy away from sex talk or mentally ill people. IT'S NOT WORTH YOUR TIME.

Other people are avoiding him because they have healthy boundaries and self respect, you do too and deserve to tell him how you feel! Stop putting his emotional health before your own. We teach people how to treat us.