Anyone who uses a historical argument with religious objections need to stop. You are misinformed.
Marriage was entirely a civil (non-religious) concept before it was co-opted by religion and sanctified. The entire idea is originally about property law. (and trading daughters between families.) Binding two people for life isn't exactly a natural concept. It was forced on the population by a governing body.
You can't say that the government has no business regulating (or performing) marriages, because it was their idea to begin with... Imagine if the church started printing it's own money, then asked the government to butt out of it's business.
edit: for the record, I support the government getting out of the marriage business, I just haven't figured out a better argument against the current ruling that doesn't include "religious" objections.