You also can't compare homosexuals to women in terms of status.
Someone's gender is not something under their control (we'll ignore the whole transgender thing here), so to discriminate against them for being of a particular gender - such as women - would be to do so based on a factor out of their control.
However, the homosexual lifestyle is a choice, and there is not only precedent for laws to govern choices, but many laws exist EXPLICITLY for that purpose (i.e. theft is illegal to keep you from CHOOSING to steal).
That's one of the reasons why I find no problem with a law preventing gay marriage.
I also believe marriage is already equal because anyone can already marry someone of the opposite gender.