On the most basic level the need for sex (not just men but women need it too) is the same physiological need like eating, sleeping, drinking, breathing and excretion. With the exception that we would literally die if we wouldn't satisfy those so while the latter five is about self-preservation the sex is for the preservation of the species, but beside this it's just the same in that regard that we feel the urge to satisfy the need when it arises, it isn't really a constant need. Or at least a healthy person's thoughts are not constantly revolving around sex. With stimulation the need can be aroused ofc. A good looking woman should grab the attention of a healthy man, but I can say similar to a delicious food, if you step into a kitchen where a slice of meat is fried it easily can start the saliva flow. Nothing bad about it.
How we act on these urges, how to satisfy our needs, what our behaviour is like is a different matter. Since humans aren't live their lives in absolute isolation, what we do and how we do it will have an influence on others. And here comes the morality which basically makes it easier to live together or beside each other, morality is kind of a social lubricant. Ofc certain cultures have different morals but there were always some taboos. For example - to see an extreme one - I don't think there was ever a society where killing could have been done just liek that as if was like taking a breath, such society would have fall apart very fast. Without morality they are. Fun fact: in our modern society there aren't any morals, there's no "official" source that would regulate it, and remind us what's good and bad. Even our laws don't say killing is baed mkay, just if you kill someone you have to give some years from your life, basically bartering them. Some crimes can be payed in money, they have a price. I can punch someone for 100 €. Is it bad? No, just a bit expensive. Frankly I really would buy a season ticket so I could punch others. People now are just flying on autopilot because our societies got used to it to have morals. Meanwhile we are bombarded with information that contradicts these earlier judgments.
Even if our acts isn't played in public, like - generally - sex, still will have influence on the public. Since our behaviour is part of us, we bring it within ourselves into the public. The act can be left behind closed doors, but our nature cannot. In our nature some things are instinctual, some learned unconsciously and some formed consciously (one can cultivate a habit), so our behaviour can be inherent even if it isn't genetically "coded". And ofc as you pointed out it can be based on decisions (but our decisions many times pre-decided by our nature, by our feelings, and not based on clear judgment of the facts).
So we bring our nature with us among other people and our motivations will be the same there what was behind closed doors. Only maybe our consciousness regulates our actions more. Or not.
Would you trust a man who can be bought with a cake? To take another example, eating. One would consider obesity kinda harmless to society. It's bad for that person's health sure, but does it harm me? Well... he overconsumes, and a burden on the resources. But there's more, because his urge to eat is a weakness. If he sees the source of satisfaction in danger, or one offers a way so he can satisfy his needs more easily or secure it, he could chose to act in a way that endangers others or the community itself. We could say it doesn't matter how he gobbles in the privacy in his dining room but he is the same person when he comes out there.
Temperance is a virtue. But when is it praised nowadays? Maybe in relation of an "exotic" eastern philosophy. But not so long ago the church itself propagated to the whole society.
Now I'm not sure where I'm going with this, started to ramble, maybe you find some answers in all this.