Not that I disagree with giving equal rights to the GLBT community, but your characterization of opposition being that it would "force the US to give homosexuals equal rights" is somewhat misleading. The opposition would be that it would again step on states rights as it is the states' right to determine marital standards.
Of course either way, it is a step in the right direction. I mean that to say that we do not allow different treatment of minorities. Why should sexual orientation be different.
"I would rather be exposed to the inconveniences attending too much liberty than to those attending too small a degree of it." Thomas Jefferson