What a challenging situation for you brundle! I don't have children, so my experience in this area is limited. I wonder though, if you might be able to find a moment with your son to share how you felt about the encounter with the mom. I'm thinking not so much how you felt disappointed in your son (he might be feeling some shame and your disappointment will make that worse), but more about how mom's tirade was making you feel inside. The more "I" statements you can use, the fewer blaming messages you'll model to your son, and he'll see how a better-functioning adult takes in and processes a difficult person. I'm thinking something like, "When she stood there and told you that you weren't good enough for her daughter, it made me feel hurt and angry, and I just wanted to give her a piece of my mind, because I didn't think you deserved to be treated that way by her. I think you would be a super person for anyone's daughter." Or, "When she said XXX to me, I felt like she was mocking me, and I thought that was unfair to me and it made me mad."
The cool thing about "I" statements is that they communicate strength and confidence, in that only someone strong and confident in themselves will take the risk to be vulnerable and reveal true inner thoughts and feelings. And "I" statements help preclude us making judgmental type statements about others. Your son has already formed his opinion about the mom, and if you say that she is this and that, it will call your son's judgment into question in a direct way, perhaps triggering shame. Then you may lose him. Revealing your reactions with "I" statements will demonstrate to your son another perspective and interpretation of the events, and allow him to modify his own judgment of the mom and the situation, in his own time. Hang in there brundle, your son is lucky to have a mom who cares as much as you do.
