You keep saying they should remain faithful [only] to their spouses, but haven't really backed it up with a reason yet. People like to fuck, a lot, sometimes with different people. They also find somebody that they love and want to spend the rest of their life with. I see no reason why these two things need to be mutually exclusive.
It would be de-facto argumentation to legalize polygamy if they are not faithful only to their spouses, if people being married still wanted to fuck with others of the same gender besides their spouse then that's legalizing polygamous marriage and given the statistics evidence does seem to be a reasonable burden of proof to marriage otherwise get common-law.
That said having too many partners does result in a significant increase in the risk of STD's and the differences in how sex is practiced between the LGBT community and the straight community especially in terms of the number of sexual partners show the impact these viewpoints have in the transmission of HIV/Aids.
While with gays the chance of having a wedlock kid who you don't know the father or mother of is 0 compared to sexually active heterosexuals that does not apply to Bi-sexual individuals who could spread STD's between sexes.
If a LGBT couple wishes to marry then they should remain monogamous and not implying that their should be a change the definition of marriage to include multiple partners (polygamy) or I guess divorce, extending from the topic of gay marriage the main reason blood transfusions are denied to the Gay community is because of the high risk of STD's and that remains true to this day even with more modern testing methods so there is a reason to ask for proof of faithfulness to their partners after marriage.
Straight people don't have to prove they're going to stay with one person only, why arbitrarily make a point that there is too much somewhere between straight and LGBT people?
There is evidence that correlates a difference between straight and LGBT groups in STD's and this is due to the increased partners they have and does NOT apply to heterosexual couples to the extent it does in the LGBT groupings where 2% represent 61% of HIV infections.
Why are some people, such as heterosexuals with multiple partners, allowed to donate blood despite increased risk for transmitting HIV and hepatitis?
Current scientific data from the U.S. Centers for Disease Control and Prevention (CDC) indicate that, as a group, men who have sex with other men are at a higher risk for transmitting infectious diseases or HIV than are individuals in other risk categories. From 2007 through 2010, among adult and adolescent males, the annual number of diagnosed HIV infections attributed to MSM increased, while the numbers of infections attributed to other risks among males decreased. Among adult and adolescent females, the annual number of diagnosed HIV infections attributed to injection drug use and heterosexual contact both decreased.
http://www.fda.gov/BiologicsBloodVaccines/BloodBloodProducts/QuestionsaboutBlood/ucm108186.htmA history of male-to-male sex is associated with an increased risk for exposure to and transmission of certain infectious diseases, including HIV, the virus that causes AIDS. Men who have had sex with other men
represent approximately 2% of the US population, yet are the population most severely affected by HIV. In 2010, MSM
accounted for at least 61% of all new HIV infections in the U.S. and an estimated
77% of diagnosed HIV infections among males were attributed to male-to-male sexual contact. Between 2008 and 2010, the estimated overall incidence of HIV was stable in the U.S. However the incidence in MSM increased 12%, while it decreased in other populations. The largest increase was a 22% increase in MSM aged 13 to 24 years. Since younger individuals are more likely to donate blood, the implications of this increase in incidence need to be further evaluated.
