Nothing says 'domination' more than doing something unnatural to another which places even a willing subject in a position of submission and humiliation.
You're assuming that politicians are the dominant ones in the activities. Sometimes it's just the opposite.
The Fifty Shades of Gray guy who's dominant in the real world doesn't need to do that in his fantasies. Sometimes he just wants somebody to spank him.
I suspect plenty of politicians are gay, because politics is like entertainment, the arts, education, the clergy, or the law, and a lot of people in fields like that are homosexual.
I have little doubt that there is more sick stuff in the halls of power than I want to imagine.