Bottom line is, society has whatever morals it has. If government reflects it, it makes no difference. If government opposes it, will do so ineffectively. Two examples; Prohibition and Reconstruction. Despite Constitutional amendments, drinking and civil rights abuses continue during those times, respectively. You could pass a gay marriage amendment, but if society accepts homosexuality, the presence of a Constitutional amendment will do nothing to change that.
Well, hell then, let’s all give up and just commit suicide since there is no absolute answer to any problem. Sorry, I don’t accept your defeatism.