OK, if you want concrete arguments:

This [the relative overfunding of HIV research as compared to other, more pressing epidemics] happens because gays have organized politically

The first thing wrong with this statement is the knee-jerk association of HIV with the gay community, which disregards the difference between the vulnerability gays had during the past century and their better standing today. Gays kept their sexual life secret because mainstream culture routinely feared, hated and misrepresented them. In such conditions they were much more exposed to STDs, because clandestinity made it much harder to establish and maintain stable relationships, and stigma gave them less incentive to seek medical attention.

Also, the antibiotic boom had lessened the fear of the old STDs, all of which were now curable. This, together with the contraceptive pill, was a huge boost to the 1960s sexual revolution, which made the 1970s a period of relaxed attitudes about safe sex. Thus, the 1980s were wholly unprepared for a new STD. The fact that the disease was first detected in the gay community is only attributable to the marginalization they already lived in. This disease can be used as a proxy indicator of which group has the least autonomy and freedom to protect itself, which makes it not at all surprising that currently the demographic sector at most risk for AIDS is heterosexual housewives.

One side effect of the AIDS epidemic was to expose the hypocrisy of having had a sexual revolution that didn't acknowledge the existence and validity of the gay experience. However, gay political activism had started well before AIDS; remember the Stonewall riots occurred in 1969.

they don't want to change their basically self-destructive behavior.

Nobody would have described the gay experience as "self-destructive" before the AIDS epidemic. The closest that you would have heard would have been prophets of doom citing God's nuking of Sodom as a scare tactic that was getting older every time they repeated it.

It is not being gay per se which kills you; it is being forced to live in secret and not having anywhere to go for help. If you take an entire segment of the population, declare them not fit for public viewing, and object to their every movement, you can't act surprised when they're hit first and hit hardest by a new disease.

But there is another, more sinister layer of meaning beneath the description of the gay experience as a "self-destructive behavior" that they "don't want to change." You're basically describing them in the same language used to demonize drug addicts, and thereby you're disrespecting both populations. Addictions involve a physical dependence that impairs proper decision-making, and accusing them of simply not wanting to change goes against the facts and against compassion. By using the same language to describe the gays, you're falling into the gay-as-a-choice trap, which is not only a myth, but an insult to their intelligence. Apart from true addictions like nicotine, ordinary people are smart enough to stop doing something that kills them. In any case, it is not their desires that's killing the gays; it's lack of legal protections and lack of human compassion. Blaming them for their desires is completely beside the point.