existentialist i think you're spot on with the children sometimes having an inbuilt radar, that certainly makes them feel creeped out by certain individuals. Even if they can't articulate why.
Being a kid in the seventies I clearly remember getting that feeling with savile and jonathan king and even stuart hall. They all demonstrated that same falseness to me...the forced jollity and the hollow laugh.They didn't ring true. In saviles case i thought he was always angry and badly masking it.
It wasn't a foolproof sense though. I thought Ken Dodd fell into the same camp, but had gary glitter posters on the wall and queued up for Rolf's autograph .