I agree that the more choices there are, the better. Neither would be for me... but each to their own.
Marriage has always been a religious, misogynistic type of ceremony... and it is not surprising it has become unpopular.
I wouldn't make a Civil Partnership the same at all, but make sure it was different to allow people different choices and a bit more modernised.
I don't think there is any more "justification" for it, than there is for marriage. But I can understand that people don't like unfairness, and if heterosexuals can get married and homosexuals can be "partners", that everyone should have the same choices.