A condom is a birth control devise, not a sufficent barrier against AIDS. The crux of the matter is sexual practices. If the guy can commit to having sex with one woman it probably would have more effect than using condoms.
We keep forgetting that. The issue in the case of marital act when one spouse is infected is using the condom in its secondary purpose, as a barrier for viruses. I wonder if the Church would not encourage the development of a non-contraceptive condom, that only prevents the infection. I do not see why such a device would be morally questionable between spouses, as it becomes merely a medical device.
It's a lousy b/c device too.