Marriage is a religious thing, according to social conservatives (Not that I totally agree) So if you give the gays benefits without dirtying the religious institute of marriage, their is no harm done. At least, that’s the justification I’ve been able to piece together, I’d love to hear others reasoning.
Marriage is a religious institution that has existed for thousands of years - before the existence of the US government, before the drafting of the constitution, before european settlers even arrived in the US. To legislate a new definition of marriage destroys the concept of the separation of church and state.First off, there has been no single definition of what marriage is throughout history. Yes, normally it goes by the one man one woman model, but there are exceptions to that. There's polygamous marriages for instance, which have existed for thousands of years as well. There's also been various rules as to how the marital relationship works, varying by religion, country, and time. Variance in rules includes who is in charge of what in the relationship, whether a divorce is allowed, etc. Point is, marriage has changed over and over again.
Second, for the government to legislate a new definition of marriage does not violate the separation of church and state. The reason for this is because marriage as the state defines it is not religious in nature. As far as the state is concerned it's pretty much a civil contract between two people. Two atheists can get married just as easily as two Christians, two Jews, two Muslims, two Buddhists, a Christian and an atheist, a Jew and a Muslim, a Scientologist and a Pastafarian, and any other combination of people who may or may not religiously be forbidden to marry. They also allow divorce whether or not the religion of a married couple allows it or not, as well as not recognizing polygamous marriages whether or not a particular religion allows it or not. If gay marriage is recognized by the state, it will be without any regard to whether a particular religion allows it or not.
Seperation of church and state only prevents the state from behaving in a manner that is overly biased towards a particular religion - they can't act as if a single religion is the state religion. In regards to marital contracts, the state would only be crossing the line if they attempted to force people to religiously accept a marriage that contradicts the religion then it is violating the first amendment. No proponent of gay marriage is asking that religious people be forced to religiously recognize any marriage of any kind as far as I know.