It doesn't sound like you have known these men for very long, are just "dating" and are getting a bit ahead of yourself (in bed)? A few dates does not a "relationship" make. Feeling sorry for the first guy is not the same as wanting to be with him or being able to do anything for him. You cannot change him/his past experiences and do not need to "do" anything to break up with him. If you would like to tell him you don't wish to see him again, send him an email or wait until he contacts you again and just say "no" to whatever he proposes, tell him you aren't interested or are doing a lot of dating right now and are not interested in going further in a relationship with him "at this time" (social code for, Don't-call-me, I'll-call-you).