I'm not sure that I agree.
I actually had a kid about 11 or so want to dance with me at a party, and it seemed like she was attracted to me (I didn't act on this). Provided a kid actually knows what's what at that age... Children that are capable of choosing what sugary cereal to eat are certainly capable of giving consent. This is called free will.
There are a number of issues though. First of all, they usually do not know what's what at that age. That is, while they can give consent, they cannot give what is known as informed
consent. "Hey little girl, would you like to have some fun? Now bend over." They are not likely to know what's happening until something traumatic has happened.
Which brings us to the second point, there is a serious question of emotional readiness. I can tell you from my brief foray into prostitution (I was kinda poor, okay?) that the age don't matter so much, it's being emotionally prepared for something. At age 29, that still freaked me out, because it wasn't someone I knew or trusted but a complete stranger. The less emotionally ready you are, the more
The third issue is the size difference. Not only the size... down there. But the fact that someone much bigger and stronger than you can basically force you if you say no.
Now. That being said, I think there is an unreasonably high age of consent. Past the age of 16, you're basically stalling for time. What I find objectionable with this is that it tends to encourage young mothers to abort the pregnancy. Abortion is rather disgusting to me. I think what I agree with are close-age laws. If you are less than 2 years apart, it should not matter if you are younger than the minimum. It's the idea of a 30 year old messing with a 12 year old.