Hmmm...
While I can see how in a perfect world prepubescents would have no reason to turn to such lengths to meet their needs. I also think that we are far from that. And I live in the EU, there are much worse places.
From the other thread, many had the opinion that one should "Turn around and run!" when approached by a underage. But will that really help anyone? ( Yes, in a perfect world children would never feel the need to do so, and yes, in the current society you will risk jail for it. ) Because in the short term it certainly doesn't, you increased the number of adults that ignored she/he by 1. It might not make things worse though.
The long term effect is much harder to predict, but I don't think that these situation are even close to outright forcible rape/molestation. Hypothetically it could have a positive long term effect on both parties.
And in extreme cases, where they are doing it to meet their basic needs (food/shelter), it becomes even more complicated. But lets just hope that in the US/EU this isn't relevant.