Lol I know exactly what you're talking about - it's why I have never joined an MG!! I know for sure I'd be the bad egg with the feral kid that all the other mothers dread hahaha :/
I agree though, I mean I've taught DD1 good manners and she's had to learn to share etc because DD2 is now scooting around yanking at her toys, but I'm usually pretty chilled about kids getting a bit rough with each other or letting them sort their own little tussles out when it comes to fighting over a toy or whatever, kwim? But whenever I'm picking up/dropping off at daycare I always feel obligated to be super-polite and put the whole manner thing on for the benefit of other mums and the daycare ladies... it's uncomfortable. Tolerable, obviously, and only for a few minutes twice a week, but yeah, I do feel the same way you do