Whats better than sex with 18 year old? Sex with eight ten year olds
Do not think it is ok to say something like this.
It's a joke. Treat it as a joke.
It is difficult to treat something as a joke when it is talking about such a serious crime. Child molestation is such a sad thing to have happen to a young child as it can ruin their self esteem for the rest of their lives. Making jokes about something like this is just not a very mature thing to do.