Well of course it is. DOMA specifies marriage as the union of one man and one woman. Like many democratically inspired laws, it allows the tyranny of the majority to affect the minority.
I'll ask again, why do we allow the government to define our lives? As a conservative, I'm against our government treating anyone differently, be they rich, poor, straight, gay, black, white, brown, etc. (Actually what I really don't understand is why so many liberals are in favor of identity politics as this is exactly what it always leads to.)