The powerful need/feeling not to try sexualizing specific people or fictional characters

Have you ever come across a person/character that you may feel deep connection, or respect, or deep admiration towards - and then, at some point, all of the sudden, they are somehow about to come in light in a sexual perspective, and then you suddenly find a strong feeling in yourself that seeing them as a sexual creature all of the sudden feels terribly weird, wrong, crazy, scary, horrible etc?

Why do we not want to see or consider some people or characters as sexual people at all? (I'm not looking at people you'd find normally unappealing to start with).
Even if we would get somehow interested at this new point of view, at least to a point, we just cannot seem to be able to cross that strange border?

Is it some kind of "ruining your childhood" effect?