See, this is at least part of why we’re getting defensive - because the underlying assumption in so much of the discourse from younger folks is apparently we’re old and senile and must have forgotten how to be moral human beings (I’m sorry, but I’m 49, and I come from a family of people who live into their nineties - I’m not due to hit senility for at least another thirty years). No, we’ve actually thought this one through, kids - and we’ve had a bit more thinking time than you guys have.
But the other reason we get defensive? Is because we can hear our younger selves in your scoldings. We can hear the parts of us which wanted to believe things are capable of being black and white, things are capable of being simple in this massively complicated world. We can hear the parts which keep arguing constantly if we just said the right thing, or did the right thing way back when, the bad thing which happened to us wouldn’t have happened, and the fact it did happen was an indicator of our personal moral wrongness. And we know how much damn work and effort and tears and sweat it took to even reach détente with this bit of us, the bit which wants to punish us for finding any kind of pleasure in life at all, and believe it or not, we really don’t want you to have to go through the same sorts of hells we went through.
There is worse evil in the world than an age gap in a fanfic - and unfortunately, you children are perpetuating it upon yourselves. As a wise man once said, evil begins when you start treating people as things - and this includes when you start treating yourself as a thing. Humans are allowed to feel pleasure - and this includes pleasure at things other humans don’t enjoy. Trying to dictate what’s “appropriate” and “inappropriate” to cause pleasure… well, that’s a step on a road which leads to things like declaring sexualities, races, entire religions, entire cultural groupings, to be anathema.
(And yes, I realise you aren’t listening to me preach tolerance. But I have to try, because if I don’t, I’m betraying my younger self too. Because she needed someone to reach out and explain to her that she wasn’t broken for not liking the same stuff as other people, and she wasn’t broken or damaged for being different. We aren’t all supposed to be alike - there’s room for everyone at the table).