Straight couples don't have to be monogamous to be married or married to be monogamous. Monogamy no more defines marriage than the presence of children does. Monogamy isn't compulsory and its absence doesn't invalidate a marriage.
Straight people are everywhere!
I am not an idiot, and I'm not a Pollyanna sort of kumbaya type.
A huge part of what animates homophobia among young people is paranoia and fear of their own capacity to be gay themselves.
Men were never expected to be monogamous.
The mistake that straight people made was imposing the monogamous expectation on men. Men were never expected to be monogamous.