I concur. I wonder, though, if he would have even heard his parents saying that if the school hadnt made a bigger deal of this than needed to be made.

A six year old kissing another isn't sexual harassment, because they have no way of knowing better. If they'd just called in the parents and explained that the behavior was inappropriate and wouldn't be allowed, it's likely his parents would not have responded with "wtf? He's six! He just has a lot of energy!"