Wouldn’t you view the analogy between the Civil Rights movement and the movement to legalize gay marriage a bit extreme? Seems there were a lot of issues being fought for and over with the former, while the latter is over a singular item.
The concepts are the same, though I would never compare what happen to people of African desent with what happens to gay and lesbian folks. While discrimination based on sexual preference is wrong, the historical wrongs of slavery, Jim Crow, segregation, lynchings, etc are far worse.
So think of it, in terms of historical wrongs, as the difference between an assault and a murder. The principals are the same, but the degree of wrong done to African Americans was far worse.