Even if every gay in the country wrote letters and made calls to Congresscritters, it wouldn't be enough to "force" Obama to do anything at all. To many Americans it would just prove that we're a special interest, which means someone to be despised and fought.
We need a Martin Luther King here, someone who doesn't fight for a particular group, but who fights for the rights of all. His success didn't come from pushing an "us v them" mentality, but from pushing an "all of us together" mentality (believe me, if it had been the former, Charleton Heston wouldn't have marched with him, nor a lot of other whites, because it would have made it a racial antagonism issue).
So long as we keep casting it as something for us, rather than standing on basic human rights for everyone, we won't have enough fellow travelers to be able to force any president's hand.