Fully lied to Disney to get my DS who was not quite 4 on a kids-only pirate adventure. He would be 4 in two weeks. So we had his birthday party 3 weeks early, then went to Disneyworld. He couldn't read yet and didn't know it wasn't actually his birthday. He thought he was four, told them he was four and was off on the adventure. I knew he was perfectly mature enough and close to the cutoff so I had no shame... plus I didn't lie to him... exactly.
I know what you mean though. We were stopped once by a lady in Walmart who was staring at my DS. He was sitting in the shopping cart going on and on about something related to Magic School Bus. He was barely 2 years old at the time. She rudely snapped that he was far too old to still be in diapers and I clearly had some issues. DS turned to her and said "I'm only 2 lady, what do you expect!" I was mortified that she thought she could just criticize a random stranger... and proud of DS for defending himself while I sat there dumbfounded!