Many opponents of marriage equality often justify their opposition on religious grounds. The essence of all this is basically the belief that gay sex (or homosexuality), is a sin. In actuality, such a belief does not actually provide justification for being against marriage equality. This is the case even if we put their premises in the best possible light.
To show why, the first thing I’ll do is grant, just for the sake of argument, that gay sex is a sin. But the sinfulness of gay sex does not provide justification opposition to marriage equality. If gay sex was their only problem, then they would have to have no problem with a sexless same–sex marriage. After all, if both parties in a sexless same–sex marriage remained celibate, there would be no gay sex and therefore no sin. Since there’s no sin, no justification for opposition remains.
Analogous reasoning can be used for homosexuality. If we grant for the sake of argument that homosexuality is a sin, then they would have to have no problem with a same–sex marriage between straight people. In such a same–sex marriage, there’d bo no homosexuality, and therefore no sin.
But of course, it’s obvious that wingnuts’ opposition to same–sex marriage isn’t really about any deeply–held beliefs, or any real concern for the sanctity of marriage, but rather due to animosity towards LGBT people. And besides, coherence from fundies and wingnuts is as likely as snow falling on Tarawa.