Gay rights may not have explicitly persued by democracies of old. But modern democratic values implies at the very least: freedom of expression equality under law and other values which may imply a different attitude regarding what gays can and can't do. Gays have been opressed for a long time. There's some momentum for this type of a sociatal attitudes and norms. So granted democracies have changed and evolved but the idea of gay rights is not an antithesis for democracy.

So in a society that sees gays as people, it's not a large leap to consider gay rights as part of a evolving definition of democracy. Same as all western "democracies" took time to let women rights be a thing. Will you argue that a contemporary democracy which doesn't give women a right to vote is a democracy? If not, then how is gay rights different?