For exmaple, a main stimulus for mail arousal is visual, and there is essentially no overlap between pornography directed at hetero men and at gays. What arouses a woman tends to be less concrete.

I don't think there's much of a social component to how visually based male arousal is.

Republicans are like fetuses: both are incapable of thought. That's why Republicans are against abortion.

I think it is obvious that people will engage in less sexual activity if it comes with higher potential costs.  The easiest thought experiment is to ask how people would change their sexual choices if they suddenly discovered that a) there was no legally available contraception, or (since this is a thought experiment) no contraception whatsoever, and b) that there was strong social pressure to marry anyone with whom you were discovered to have had sexual relations.

But would people actually have less desire?  

In Ancient Athens, women were basically shuttered within their homes, except for special occasions.   There is not much literature about it, but I assume lesbianism was common and accepted.  What is certain is that male gay relationships, at least among the aristocracy, were accepted as normal, and even idealized as superior to relationships with women.  The shame component was significantly diminished.  How did this effect sexual behavior?  How did it effect desire?  

I don't know the answers, but it gets to the social v. hardwiring question.

It also gets to the social policy question.  Before you can answer the question of whether certain sexual practices should be discouraged through social policy (like criminalizing contraception) you have to ask whether it can actually change behavior...or will it just push it underground...create a black market, etc.  

One area where we regulate is based on age.  The hope is that by creating strong social taboos and legal penalties for having sexual relations with teenager minors, people will not do it.  And, it is also hoped, that people will not want to do it.

Since most people agree on the wisdom of this goal, the question is about the effectiveness of the taboo and the laws on changing both behavior and desire.  

But for more controversial taboos and laws that are sought by social conservatives (about homosexuality, sex out of marriage, and contraception) we could possibly make social science arguments that say, even if this were a desirable goal, it won't work all that well.