In Britain, like most other western countries, our laws enshrine a very warped sense of rights. If we genuinely cared about equality, and respected people's rights as individuals, the law would have nothing to say about the various groups that people can be divided into. Our rights wouldn't be constrained, but nor would we get any special privileges for belonging to one group or another.
Contracts, and the ability to enforce them, are a basic pillar of civilised society. In the absence of Rothbardian private justice, one of the legitimate functions of government is to arbitrate and enforce contracts. Marriage, whilst for many people religious in nature, is just a particular type of contract in the eyes of the state. It carries implicit agreements about child custody, insurance, inheritance, and so forth. There is nothing special about marriage that should make it any different to any other type of contract—in the eyes of the state.
Except that in the US, for some reason, there is a strange moral attribute to the marriage contract. Homosexuals cannot enter into this contract with each other. They are specifically and specially debarred, in a way that is utterly exceptional in a country that usually only refuses to recognise your right to contract if you are (a) a child, or (b) non compos mentis. There is nothing, even, to stop a gay person from marrying someone of the opposite sex. It’s only each other they can’t contract with in this way.
The state is not there to enshrine the religious or moral connotations of marriage; in fact it doesn’t do so for straight people at all. Straight people can contract marriage in front of the state without ever getting close enough to sniff a priest or a rabbi or an imam.
So why should gay people be denied this same legal status? The US government isn’t trying to pretend that gay people are as incapable of consenting to agreements as children or the mad; it isn’t trying to pretend that straight marriages always and everywhere carry a moral or religious weight. It’s either (a) bowing stupidly to pressures from people who would use the government to impose a moral sanction, or more worryingly (b) sees nothing wrong with making arbitrary exceptions to normal jurisprudence when it suits.
Catholics would not be forbidden from marrying the Sovereign, but nor would they get any special protection against 'hate speech'. Homosexuals would be free to have sex with, and marry, any consenting adult they like, but they would not be entitled to anti-discrimination treatment in the workplace. Women would be truly equal to men; neither paternity nor maternity benefit would be provided. For it is also important to treat parents, childless couples, and single people equally.
All people would be equally free to denounce others as toffs, ponces, chavs, and pikeys; kafirs and kaffirs; not to mention coconuts and watermelons. Hopefully, as a matter of basic human decency, they would avoid causing unnecessary offence, but it is not the job of the state to compel politeness.
We are all individuals, and the law should treat us as such.