I will, until I am blue in the face, defend any adult’s right to enjoy whatever silly, all-ages thing they like without being hassled for it.
But there’s a flip side to that right: As adult fans it is absolutely our responsibility to make sure our enjoyment of that thing does interfere with a minor’s ability to enjoy the same thing in a safe space.
That means putting warnings on fics that have adult themes, that means not posting porn in the main tags, and it absolutely positively means not having any inappropriate interactions with minors you meet on this website, even if it’s their idea.
This is the basic price of admission every adult has to pay for entry into an all-ages fandom.