I agree with your comment, first there are many spaces on the internet where there is content exclusively for children and #nostr is definitely not the place.

Second, those who must protect and take care of what you want the children to see or consume on the internet are the parents, not the others.

Third, if a child wants to search for and consume porn, he will do it anywhere. Rather, you have to educate and talk about the subject with them and not demand that others take care of what they do or publish.