heterosexuals would be just as promiscuous if men could talk more women into bed. The only reason why hetero men have fewer sexual encounters is that they must negotiate more with their perspective partners. Women have different attitudes about sex than men. Lesbian women are, by contrast to gay men, not very promiscuous. Most form long term relationships.

If promiscuity is the issue you are concerned with, than why are you opposing monogamy among gays. If anything, to be morally consistent, you should be encouraging this. Many straight people marry to obtain citizenship. Every institution created by humans has been abused at some point by some percentage of the populations. Would you be equally willing to punish the straight population as a whole for the actions of a few? You are obviously saying that groups have collective responsibility for all the actions of their members. Do you know where this logic leads? And how absurd the consequences will be?