I think in this case the burden of proof is on both of us. We both have stances, and both stances have precedent. In fact, you are the one challenging the current status quo, so if anyone the burden is on you.

I'm not really sure why American Scouts would be clueless about girls, considering that almost all of them go to schools with girls, participate in other clubs with girls, etc. etc. If they are not interacting with girls, I think that is more a failing of their other social activities, not a failing of the scouts.

Fundamentally, I think the idea is to have some aspects of life / growing up where sexuality can be largely ignored in pursuit of an arguably more constructive environment. i.e. teenagers have a whole lot of hormones, and focus is easier to maintain when you're not thinking about a tumble between the sheets with the person sitting next to you. That's just how our brains are wired.