As I am not gay, I do not have a particular interest in supporting or opposing "gay rights". An objectivist would support or oppose something based on what selfish value it brings to them. I gain very little either way.
What I am against however, is the promotion and glorification of gays in media and culture.
In general, I view marriage as something which does not require special intervention and regulation from government. To me, it is a business contract, and should be treated as such. And more importantly, it is a contract which mostly involves only the two persons entering it. If two adults want to enter into a contract, whether it is marriage or something else, I think the government has no business stopping it.