I'm sure the "love and commitment" crap got some people warm and fuzzy, but as far as I know, Federal laws don't care if one is in love or committed to the person that they married. The only reason the Feds care whether a person is married or not is give them access to a variety of benefits/protections that lawmakers have created over the years. This opens the door for more people to have reduced income taxes, eliminated inheritance taxes, Social Security death benefits, etc, etc.
What upsets many people about this is that they view marriage as a religious institution and feel the government shouldn't be involved with it at all. What other instances are govt benefits tied to a religious ritual? IMHO, a better way to settle this issue would be to purge Federal law of anything related to marriage and have the government institutions only recognize civil unions. That allows the govt to define who is eligible for civil unions, lets the religions decide terms of what they call marriage, and eliminates any potential church/state contention which is the root of most of the opposition. It's what Mexico does: people can get a civil union, religious marriage, or both (potential for two anniversaries and two parties).