I know the chances of you endorsing that rally were slim, but I felt I had to point it out regardless. Manif Pour Tous isn't a nice protest group. Interestingly, they often inflate the number of demonstrators they draw.
I've had a similar debate with my brother plenty of times. He was a hardcore Bernie supporter during the primary, while I preferred Hillary. Though, both of us pledged to vote for whichever won the nomination. He still likes to call many Democrats "corporatist." While Democrats do take money from big corporate lobbies, I think it's silly to use that label in the context of our current Republican party.
On a side note, many far right nationalist candidates are nominally pro-gay. Like Trump and
Le Pen, they put forward an affectation of not caring much about gay marriage or similar rights. They have a veneer of libertarian talking points. Often, their "support" of gays is used an excuse for their xenophobic policies. IE, "we need to stop refugees because Muslims are anti-gay,"