Male-male Promiscuous sexual behavior is the worst, very dangerous in fact by nature. Our tax dollars go to pay for HIV drugs for them.
Male-female Promiscuous sexual behavior is next in bad for health.
Female-female Promiscuous sexual behavior (which I assume is rare) is the least problematic of the above because there are few fluids exchanged.
It seems that sexual relations limited to the same sex is rare. Many(most?) so-called homosexuals are bi-sexuals.