For equality? What is equality? Those in significantly different situations are not “equal,” just like we discriminate against other forms of marriage.
Why is polygamous marriage wrong if homosexual marriage is right? (Again I find those who support homosexual marriage have not defined marriage, and it is just whatever they feel is right, and have no definite meaning, thus homosexual marriage is fine, but polygamous marriage and adult incestuous marriage is wrong, but not based on any sort of understanding of marriage).
I was not speaking in religious terms but merely secular. The state recognizes marriage for some reason(s) surely? if we look we can see that the state supports married couples by giving them benefits which will hopefully encourage people to get married and then stay together. Because this is what the state wants. Children growing up in stable environments so they can become stable productive workers. Obviously these benefits are not the main drivers of marriage, so of course people break up, then marriage often protects the otherwise disadvantaged spouse and children (or at least they were supposed to).
And you are wrong, true marriage can happen between anyone (male and female), Catholic or not. Even sacramental marriages can happen between 2 non Catholics who are baptized. But again, I was speaking in purely secular terms in why the state should support, recognize, and give benefits to people who do not fit the reason why the state recognizes the institution in the first place.