How should I handle his mistake?

Recently, my boyfriend's ex-girlfriend kissed him. He was distraught and is deeply apologetic. I forgave him and am trying to reassure him that everything is okay, but all of his old friends are trying to make the issue seem worse. They seem to want us to break up, and I am constantly on the receiving end of subtle nastiness from them about he and I. If I get angry, he freaks out and overreacts entirely, talking about how we have to break up because I deserve better. I trust him, but still wonder if I'm likely to end up hurt after all this. What should I do?