In a civilization with same-sex legal marriages, when a man refers to his "husband" and someone says, "he's not your 'husband', he's your 'partner'", it's clear that it's the second person who is being an antisocial ass, even if one might not like to admit it.
In a civilization with same-sex legal civil unions, when a man refers to his "husband" and someone says, "he's not your 'husband', he's your 'partner'", the argument that the first person is being pushy for insisting on "husband" is going to have a lot more popular traction.
This is one reason of many that they are not alike.
