I'm at a soft play with my DS (a naice one so that's not the AIBU!
) and there is a little girl who is about maybe 3-4 playing in the soft play.
She is in a nice top and skirt. The skirt is quite short (but not inappropriate (it's a flared frilly number and is actually quite cute!), and she isn't wearing any tights or leggings underneath.
The mum is sitting at the side shouting in at frequent intervals "PULL YOUR SKIRT DOWN XXXX, I CAN SEE YOUR PANTS! THAT'S NOT NICE!"
Now, the little girl is looking increasingly distressed with every bellow - and has stopped climbing up onto the high levels and is just sitting in the ball pit looking miserable. 
AIBU to think that if you put your DC in a skirt (or allow them to pick a skirt) knowing they are going to soft play, then you shouldn't bellow at them every 2 minutes! Knicker flashing is almost guaranteed - and no one really cares!
Feel really sorry for the kid, and feel I should tell the mum to let her play in peace! 