You are seeing through your own lens. The propensity is there in all children, but all pre-pubescent children certainly aren't sexualized. It ususally happens early because of either having been molested, or seen others sexually acting, or been exposed to sex on TV or movies.
Pre-pubescent children are certainly curious and maybe play "Show me yours and I'll show you mine" but sexual acts? That is not normal for little children.
Sexual acts? I guess it depends on how you define it. I only refer to the capability for rudimentary sexual sensation, not to "oral sex" or other acts. I don't look at the capability as being "sexualized" only the acts, but if you catch your kid doing something that troubles you, it would be helpful if the reaction was proportional.
But you did mention seeing someone else do something of the sort. Well, surely there are many kids who've walked in on their parents, if only once. Even if they were never exposed before, certainly that could impact them. Then all that protection and sheltering would be for naught. Seems pretty fragile to me if all it takes is seeing something at a young age.
Perhaps the earlier poster was correct in that I chose the wrong thread. I kind of assumed people agreed on Kinsey so I wanted to have a more spirited conversation rather than an amen chorus. I apologize if anyone felt my remarks were not thread-appropriate. I really didn't mean for it to be "all about me" or for people to misinterpret what I meant.