I (21M) have a friend (22m, I'll call him grey) and my friend recently got mad at me for not treating a guy he was talking to (22m, I'll call him Sam) like how I would treat any of my other friends. Backstory they were talking a few months back and Sam was being manipulative towards grey and just a cold b**ch then Sam just vanished and didn't speak to grey until recently (Sam has done this twice disappearing and reappearing using grey to attempt to fill a void I guess). There was a lot of other stuff but the way Sam treated grey put him into a depressive state and lead to him doing substances and having an addiction for a few months making all his friends worry. Recently Sam just reappeared into greys life and now they have been getting along which is great I guess but he made grey feel a way the first few times they were speaking which didn't sit right with me. Anyways the other day I was scolded by grey for not treating Sam as a friend but rather acting "like a stranger" to Sam and not treating him how I treat my other friends. My whole reason for not liking him is about what he has done in the past and now Sam is apparently having problems with his current girlfriend and just miraculously reappeared just doesn't sit right with me and I feel like he's gonna pull something

I feel bad for not treating Sam like a friend but after what he has done to grey I can't see myself being in a friendly state with him. Thank you for reading and apologies if some stuff makes no sense English isn't my first language