That again presupposes that Maxwell is just after fucking Joan, instead of fucking in general. He could just walk down to the nearest club or something. And the fact that he is a Maxwell means that he's probably much more apt at procuring samples of said limited supply of booty, and perhaps the Martins have to become Maxwells to some degree to be able to compete. That wouldn't help matters.
Joan represents anyone STD-free in general. Who else is Maxwell trying to fuck?
Maxwells don't have any special ability to get laid (even if they do, it doesn't affect the argument), they are just those that go out and look for multiple partners while STD-plagued. Regardless of their methods, they will tend to get the girls if the girls are there. In order to make it so that there less girls for the Maxwells (who would give the girls STDs), more Martins need to start nailing some chicks so that there is less supply available to the Maxwells.
Consider another hypothetical situation on a micro scale. In a bar there are three Joans (girls looking for sex), three Martins (conservative guys who do not have STDs) and three Maxwells (guys with STDs looking for sex).
In the first, original situation, the Martins stick with their conservative nature and do not try to get with any girls. For religious or moral reasons, they decide that Chasity and drinking is more their style. Thus, the Maxwells and the Joans all hook up. In the morning, we have 3 new people who now have AIDS (all three Joans). This is not the social optimum.
If, for whatever reason (the author talks about different incentives in the article, but that's irrelevant for now), the Martins change their minds and decide they want get laid today. Now, the Maxwells have competition and there is scarcity concerning booty resources. Lets just say that 2 of the Martins succeed in hooking up with Joans, while the 3rd Joan was reckless and got with the 3rd Maxwell. 1 Martin goes home disappointed, and two Maxwells fail to spread their plague. In the morning, we have only 1 new person with an STD. This is closer to the social optimum. This is a simple example because the ratio of 'Fucking-Martins' to 'Saved-Joans' is exactly 1:1, but the principal behind the example would be the same regardless of the ratio as long as neither side is 0 (1:2, 2:1, 3.4:2, whatever).
It is important to note, however, that although it is better to get these Martins into the fucking gaming than keeping them out of it, we don't want them to get
too involved in the game. Maybe they should only come to the bar twice a week, instead of 4 times a week like the Maxwells. The reason for this is although the 'Joans' are STD-free, there are also 'Janes' who may have their own STDs that they can give to the Martins. If the Martins start fucking as much as the Maxwells, they are likely to eventually to sleep with a Jane instead of a Joan, get AIDS, and become Maxwell's themselves. There is a socially optimum point in between the conservative Martin level of fucking and the Maxwell level of fucking.
As long as Martin's fuck less than Maxwells, it would be socially beneficial to have them in the fucking business (the degree to which they should be involved to optimize the social benefit depends on the aforementioned ratio). Even if they do get an STD, they fuck less than Maxwells do and thus will not pass it on to the same degree. In this regard, they are more likely to 'save' a 'Promiscuous Pete' (guy without STD that likes to fuck) from getting an STD and thus becoming a full-fledged Maxwell.
Remember:
Maxwell = Guy who fucks alot with STDs
Martin = STD-less guy who doesn't fuck alot
Promiscouse Pete = STD-less guy who fucks alot
Joan = Willing girl without STDs
Jane = willing girl with STDs (my invention)
It's easier to use names than to write all that down every time, but those are the defintions of the terms. If you misunderstand those, you are going to misunderstand the author's argument.
I hope you meant to say less sex, otherwise you'd be engaging in a false dilemma there. And why yes, I would take less sex over a significantly shorter and not to mention much worse life. Hell, I might even take no sex over that. AIDS ain't exactly all flowers and green meadows.
You misunderstood my question, and thus answered a question I did not ask. I was trying to apply what the situation would be on society as a whole (long average lifespan with no sex outside of marriage/long term relationships or shorter average lifespan with more sex) to an individual case so that you could determine which was better. If one case was better for you, as an individual, I could expolate that into what would be best for a society by the same logic. Economic utilitarianism generally has that quality. Sure, some people will gie young, but if 1000 people get lots of sex in their life, you have to weigh that in an utilitarianistic manner. I was trying to get you to weigh the two sides without directly putting a human face on it (which distorts the results from an economic/utilitarianistic perspective).