Andy Francis and Hugo Mialon, both at Emory, report their latest research:
We empirically investigate the effect of tolerance for gays on the spread of HIV in the United States. Using a state-level panel dataset spanning the mid-1970s to the mid-1990s, we find that tolerance is negatively associated with the HIV rate. We then investigate the causal mechanisms potentially underlying this relationship. We find evidence consistent with the theory that tolerance for homosexuals causes low-risk men to enter the pool of homosexual partners, as well as causes sexually active men to substitute away from underground, anonymous, and risky behaviors, both of which lower the HIV rate.
That piece has recently come out in the Journal of Health Economics.