I think following is an apt analogy to the gay marriage debate. Let’s say we were still in state-established church times (some are). We’ll call our church the Church of Officialdom. An easily recognized religion with the worship of one or more deities, liturgy, rites, edifices, etc. However, as a state-established Church, it enjoys the privilege of taxation. Whether you believe in its tenets or not, you are taxed to sustain it. This is very much how things were in Europe and the early US, and still are elsewhere, I understand.
In any event, this church performs all official marriages and the only state-recognized marriages are those performed by the Church of Officialdom. And because this church only marries heterosexual couples, and only monogamously, at some point in time homosexuals and polygamists begin petitioning the state to force its church to also perform their marriages.
Is this the proper demand to make? No. The proper demand would be to separate the church from the state. To remove its power of taxation and influence on the state on the one hand, and the states power to influence the church on the other. Only “the separation of Church and State” will satisfy the demands of equality and liberty.
Likewise, then, only the separation of Marriage and State will satisfy the demands of equality and liberty. Forcing everyone to recognize your conception of marriage, be it hetero- or homosexual, mono- or polygamous, is absurd, and contrary to the demands of equality and liberty. Will state-recognition of all types of marriage equalize things? Yes, but it is only equalizing the serfdom of everyone by empowering the state to make such determinations. The only correct demands are those for equality and liberty.