ex girlfriend probs

Sooo my boyfriends ex girlfriends husband just messaged my boyfriend with this long message about how she cheated on him and shouldn't be surprised and asked what went on between her and my boyfriend because he heard a lot of shit but the ex denied it all to him.. Now this personally pisses me off so much because we have been together almost 3 years and she was such a peice of shit to him, she mind fucked him.. Cheated on him, used him. And now this is all getting brought back up.. Like why would he come to my boyfriend of people.. I'm so livid.. Is it wrong of me to want to message this guy and get to the bottom of it or should I stay out of it?