He's presenting it as if I'm saying "Well, we've decided we can screw people of the same sex now, so why not kids as well?" which is not at all the case I'm presenting. My position stems from a few points.
One, this sanctification of children is actually a historical rarity. Civilizations - many of the greatest, most enlightened, and most important - in history have arrived at a point where sex with children is OK in certain circumstances. What do we think is so special about our culture - ESPECIALLY today - that makes it impossible we'll arrive at the same point? Considering what's going on in our culture at the moment, I can't help but feel like we're getting ever closer.
Two, the idea that there are sacred cows in our society, things which we cannot question, areas we cannot transgress, died with God, so to speak. We live in a time where if a case can be made for it, and enough people want it, society will follow suit and deem it permissible. Ask yourself - what is the absolute stumbling block that prevents us from taking this step now? A century or two ago, someone could say "Well, God says it's wrong" or something like that, but the metaphysical underpinnings of absolute morality are gone.
Three, relations between adults and children and relations between adults of the same sex are obviously different. I did not say otherwise, suggest otherwise, etc etc... The problem is that they're the same in one way which is very important here - both have been, in relatively recent times, totally impermissible in our culture. The issue is, one of them is no longer so - so one utterly impermissible thing has become permissible. The arguments that got us there are going to be different but, again, what is the absolute, inviolable case that is going to prevent the normalization of the sexualizing of children? There isn't one. That has been done away with. The idea of an absolute morality is dead and, with it, clever people can shift culture through discourse, argument, and all sorts of campaigns and lobbies and other methods until the standards shift, bit by bit, and the impermissible becomes permissible.
This is not a phenomenon without historical precedent. The cornerstone stumbling blocks, in our culture, that would have prevented it are either gone or crumbling. After that absolute framework allowing for the sacred, non-transgressable space is gone, it's just an issue of culture creep.