macmam, yes, of course it's in people's best interests, but since when do human beings act in sensible thoughtful ways all the time?
The whole of the Christian religion is founded on the understanding that people don't always make the sensible choice.
I think telling a married couple to abstain from sexual relations for the rest of their life is screwy in the extreme, tbh, and I can't think of anything more akin to sticking one's fingers in ones ears and going 'lalala'.
Abstinence is absolutely sensible, I truly believe encouraging it as part of being a responsible human being is a reasonable thing to do. But without education about the other options, it's untempered idealism that can seriously damage.
Because what you're saying is 'Unless you hold to my ideal of sex within marriage alone, I don't really care if you end up dead from infection.'
Besides, all this is assuming that everyone engaging in sexual activity with total autonomy - what of the woman with an HIV infected non-Christian husband who has no investment in the idea of not having sex with her out of love (and tbh, many Christian men would have a problem with that idea too). Under abstinence only programmes, she's stuffed, isn't she?
What about woman who relies on prostitution to make a living? Improving the economy to the point where she has other options takes time - what the hell does she do in the meantime?