They are right of course. The responsibilities of the government are to protect private property rights, uphold the rule of law, represent the concerns of citizens on an international level and to maintain infrastructure. These are the proven competencies of the government.
And to stop gays from marrying each other.
Well, in my ideal world marriage would be solely the domain of the Church, and therefore the ability of gays to marry would be stopped by the Church, not the state. But for the purposes of this discussion stopping gays from marrying each other can be fitted in under upholding the rule of law.