Well the term 'Marriage' in the US is a legal condition between an opposite sex couples,
regardless of what you think ought to be.
You don't even have to be religious to be considered married before the US government.
What you do at your place of worship, or how you interpret whatever religious document is your own affair.
'Civil Union' and/or 'Domestic Partnership' in the US is a legal condition between same sex couples.
The actual rights of such civil unions vary from state to state.
In states such as CA, the rights granted to civil unions,
are more or less the same as the rights granted to a legal marriage.
Civil union - Wikipedia, the free encyclopedia
For the most part, i think one of the main controversies surrounding 'Civil Unions' is about recognition
(if other rights are already equal).
Same sex partners want their relationship to be recognized as a legit Marriage by the US goverment.
The lack of acknowledgement, is in itself an inequality.
This was, imo, the focus of things like the passing of 'Prop 8' in CA during 2008.
Personally, I'm generally ambivelent to labels.
I don't see the big deal either way.
If that's the only thing you're protesting, then imo things really aren't so bad.
Things aren't going to change one way or the other.
Ppl are going to acknowlege a relationship as legit or otherwise according to what they believe in,
regardless of what the government recognizes.