Well if someone would stoop to levels of knowingly sleeping with a married person I'm sure they could find a reason to stoop to shaming or blackmailing the married individual too. If someone was innocently led to believe their partner was single I think they'd probably be too shocked from the revelation to think about anything else. Least of all shaming the person. I guess shame them for being a jerk and not married.
I don't really think anything else relates to the act though. The gender nor sexual orientation is really a key factor in the decision making of an individual. I guess being bisexual has more temptation and a greater pool of people to sleep with, but little more than that.