I think that your personal rule is great, but, the thread's title asked for opinions on the favorite sexual positions, and, in doing so - straightforwardly and without any nuances of meaning - it put you on notice about the content of the post. So if you refuse to answer casual sexual questions, and, moreover, find the question itself an invasion of privacy, it seems that you should not have clicked through. You did click through - in order to

1) form an opinion about the visual, as expressed on the original thread and the current thread,
2) side with the policy on censoring web content employed by the administration of the college attended by one of the original thread's participants,
3) post on both threads

- you must have clicked through.

So if you were put on notice, and you had your own policy on what kind of questions you would answer, and you felt that the question was an invasion of your privacy, why did you click through?

Clearly, the site administration does various things in an effort to put us on notice - the forum is described as being "frank" and you are advised not to read it if the content disturbs you; there is an option to block the forum from view - say, mentions of SI generally disturb me so once I found out about the forum blocking capability on the site, I immediately blocked the SI forum, so I no longer see the latest SI post when I scroll down the list of forums. So the site administration tries to be helpful.

That said, there is a limit to what it can do while trying to be helpful: if you click through against your own policy and despite being put on notice, I do not know what the administration can really do to protect you, because your clicking actions are completely outside of the administration's control.