A little embarrassed and annoyed

I spent the day in Bakersfield, ran some errands and met some friends for lunch. We all have little boys so we'll go anywhere with a play area. (Not that there are any good play areas in northwest Bako), Del Taco is about the only one. Which occasionally gets busy (okay every time I've ever been). Caleb and his friends are apparently a big gang of meanies! I know he can be brutal, I have seen him in action... but here is why I'm annoyed...still...hours after the fact... I really believe he is innocent in today's "incident". Are you wondering what happened yet?
There was another group of kids on the play apparatus (I swear there were like 10 of them) and at one point it looked like ALL the kids were crammed into the end where the big bubble window is. Except Caleb, he was down by the door playing with his cheesy Del Taco toy. And I saw him with my very own eyes. Pretty soon the "other" group came tumbling out, all except one, who had been yanked down by the kid "in the blue shirt" and the kid in "the yellow shirt" causing him to bump his chin,(No blood or tears). No parent actually saw any of it. Caleb was wearing a blue shirt.... as was one of his buddies and the other was wearing the yellow shirt.
I know as parents most of us have been in this situation, and I think personally I would say, hey boys are rough but they were not trying to be mean. Actually I think I probably have said that... maybe that's because I don't like confrontation. Not so the other child's mom. She marched over and told me what Caleb did, and I of course said "Gasp, Not my child!" Okay not really but I'm pretty sure that's how I came across. I think what I said was something like umm he wasn't up there. In my head this is how it sounded, "What the heck are you talking about, HE wasn't even in the play thingy!" Then she informed me it was three minutes ago when he was up there,( really? I watched all the kids clearing out of the tube and it was maybe one minute ago) and that he hit the baby earlier. (Caleb has no problem walloping bigger kids but he tends to steer clear of littler ones, I think maybe he is afraid if he shows any kind of interest, one might show up at his house and displace him or something.) At this point I'm thinking; lady you have no idea what you are talking about, but what I was doing was, putting Caleb's shoes on and telling him it's time to go and he should apologize. All the while a bratty little girl stood right in front of me and told me my little boy was so mean to everyone and he shouldn't do that. I wanted to say "tattle tales don't end with many friends" instead I just ran out of the place. It really was time to go, but I feel like I got chased out of Del Taco and that is part of why I'm embarrassed! Caleb cried when I told him to apologize and said "I didn't do nothing mommy!" And really, I'm sure he didn't, at least what he got blamed for.
I think more of the embarrassment is because when someone approaches me like that I automatically get defensive and feel like I'm being told I'm a bad parent. (Yes I am a wimp). Which was probably not the intention, and I do realize I should just let it go....so here is me: deep breathing and letting go! Sometimes I wish I had a cartoon bubble above my head with the words I really wish I was saying, but I guess mostly that would be a bad idea. Very, very bad.