I'm going to be blunt with you, mostly because that's my way of saying things but also because i believe you need a cold shower of objectivity right about now: your first phrase is correct, you are overreacting and even worse, you're starting to push people away. Both of your friends, were the way you describe them long before your break-up and you accepted them the way they are, with their highs and lows, even more, once you know a person for such a long time and in such detail, you can anticipate or at least have a idea about how they will react in a given situation. The catalyst in this episode is the fact that they "dared" to invite your ex out and at the moment this incident doesn't serve your interests in any way : read your other "seeking my ex's attention" thread, the one about you being worried for his future and his relationship with his mother. You've mentioned this encounter there also, but in different light, this time your friends were the good guys and they were serving your interests, because by them you would have kept an tab on your ex's whereabouts. Now you realize that there might be a bigger danger in them contacting your ex and you blow them both out of the water trying to pitch it on past, well known and accepted by you, facts. To me, it's not only unfair but also very unhealthy to react in this way towards them, based only on the fact that they invited your ex out ....time will pass, you will heal and you'll be starting to see that your friends highs outnumber their lows (like it was till now) but they might not be there anymore because you've pushed them far away.
The lesson to be learned here is that people move on and social interactions evolve ... you spoke highly of your ex's mother but the day will come when she'll choose listening to her son and accept him the way he is now (without you or with somebody else), cutting you out of the picture to preserve her mother-son relationship...what then? you'll feel betrayed by her also and pass judgement? You cannot control what others think and the choices they make and frankly i was never too fond of imposing "friends embargo's" (you are not allowed to interact with my ex because we broke off) - friends aren't wolf packs, nor servants, nor troops to be moved around the battlefield.