Actually, if we refer to male homosexual behavior specifically, it isn't. Male Homosexuals, who represent a small percentage of the US population, spread HIV faster than male/female heterosexuals combined. And these are male/female heterosexuals who participate in high risk sex.
Male-to-male sexual contact 454,106 total infections
High-risk heterosexual contact 164,850 total infections http://www.avert.org/usastatg.htm
The fact of the matter is, assuming equal promiscuity, it is far easier to spread HIV through Anal sex. Your chances of getting HIV through heterosexual sex are rather low, even if you aren't using protection. Males having unprotected heterosexual sex have an even lower risk than their female partners.
Thanks for the information. I didn't know that.
"The fact of the matter is, assuming equal promiscuity, it is far easier to spread HIV through Anal sex."
That is correct. The seroconversion rates are approximately:
Receptive anal intercourse: 50/10,000 (fifty per tenthousand contacts with an infected source, assuming no protection)
Receptive penile-vaginal intercourse: 10/10,000
Insertive anal intercourse: 6.5/10,000
Insertive penile-vaginal intercourse: 5/10,000
"Your chances of getting HIV through heterosexual sex are rather low, even if you aren't using protection."
Well, they are rather low compared to the risks involved with childbirth or needle sharing, they are pretty damn high compared to a monogamous relationship between two seronegative partners. Your risk as a man having unprotected insertive sex just ONCE is about the same as having MS (multiple sclerosis). But you wouldn't tell the MS patient among your relatives that statistically speaking he should be healthy.
"Males having unprotected heterosexual sex have an even lower risk than their female partners."
Which again can be halved by circumcision. However the main reason why unprotected heterosexual sex has a lower risk for the male compared to homosexuals who do not have receptive anal intercourse is the lower HIV prevalence amongst heterosexuals in western nations. However, if you are as promiscuous as Tommy Morrison of Rocky V fame or live in a state like South Africa that pretty much evens the odds.