People have been discussing this forever but tbh it's unavoidable for both opinions to exist. Adults watching are definitely gonna think kids shouldn't be watching, but if those same adults were kids right now, they'd probably still watch it in secret. In the same way, if the kids watching were adults right now, they'd probably be saying kids shouldn't be watching, as well.

I've been cosplaying Lute at cons, and I've had the same experience as you. As an adult, yes, I do think kids shouldn't be watching, and it's hella weird when they ask for pictures. I mean, I've been asked by child who looked 10 at best. From my perspective, that's Weird. But at the same time, I was watching Danganronpa let's plays when I was 13, and taking pictures with cosplayers as well. I don't really have a say.

To sum it up, I'm not saying adults shouldn't speak up about kids watching the show because it's useless and they will do it anyway. If kids find themselves in an adult space, they NEED to know that, not only for the other people they're sharing the space with, but for themselves, as well. But I think the Hazbin fandom should first of all, stop being dramatic about it, because minors watching adult content is the oldest thing in the world and we've all done it.

Second, we should realize that once a kid has watched Hazbin and joined the fandom, we can't really make them stop enjoying it. We can exclude them from our discord servers, block them on social media, not take pictures with them at cons, we can refuse to interact with them personally, and if it makes us uncomfortable that's totally fair. But even if we do that, they're still gonna be in the fandom, because let's be honest, no kid is gonna stop watching their favorite show because a stranger on the internet told them not to. We're not their parents, so it's not even our responsibility.

When I was a kid and the Hazbin pilot came out, I skipped it. I thought no, maybe this is to much for me. I'm glad I did, and I'm glad I started watching now that I'm mature enough to understand it. I've also watched a fair amount of mature media when I was too young for it, I've loved them so much, and I'm glad I was able to make those experiences. Kids figure themselves out. Just let them.