1. Thread title. Says how you feel about it. Accept that.
2. You should probably forgive the guitar player. Accept his flaws/weaknesses for what they are, pray you can try to be better than that. Understand that forgiveness is for the forgiver, not the forgiven. Let that s*** go - It's toxic and all it does is give someone's BS free rent in your head.
3. Just because you forgive someone doesn't mean you let them back into your life. Only you can decide if, and under what new boundaries/circumstances.
4. Here's the hard part. People aren't usually convinced of something without a kernel of truth to it, no matter how big a jerk the convincer. If it were me and if I decided to give the guitarist a second go, it would be under condition of an in-person sit-down with guitarist and drummer.
I'd ask what specific issues they had with me, asking them to be honest, then I'd shut up and listen. When they were done talking, I'd ask them what I'd need to do to fix that, then shut up and listen again. Then I'd decide if it's something I was willing to do. If not, no need to go to the next step. If I were willing, I'd let them know, then follow with, "There are some conditions of my own that I'd appreciate knowing if you're willing to accept so we can move forward." Then I'd detail the why & what of the conditions.
If interrupted, I'd smile and say, "I'll listen to you when I'm through speaking" and continue, trying to be concise and avoiding hyperbole. Then I'd ask again, "Are you willing to accept these conditions?" If they tried to talk around their answer, a simple "I'd love to hear more details, but first, are you willing to accept these conditions? Yes or no." Rinse/repeat. Then after three strikes, if they continue to talk around it, I'd have my answer. At this point, it'd be time to stand up and say, "I don't think this is going to work for me. I wish you guys all the best." and leave.