I would expect that children see genitals of other sexes at home, mommy, daddy, brothers and sisters.
Genitals are not bad, or dirty, or evil. They are just another body part that most people like to keep private. Seeing some that are different than yours should not be traumatic. If it is, you got bigger problems.
And for the most part, I doubt any one is seeing anyone else's genitals in a stall in the bathroom, or even changing clothes in the locker room.
I don't know what you guys are doing in bathrooms or locker rooms but I think its totally different than anything that I have ever experienced.