In general, I don't understand why they need to have a marriage anyways. Why not just get domestic partnerships granted at the federal level? They'd get much less flak.
Sure, maybe same sex relationships can be artificially generative, but this is no where near the capability or likelihood to equal the basis for traditional marriage.
So, same sex relationships should not have the same benefits that are accrued by a generative relationship, since they do not require them and are thus just squandering resources.
Emotional issues are important, but they should not be the bottom line in a situation that clearly has a functional basis. However, the pro side seems to be mainly emotive in their driving arguments.