If the word “one” is not specific in the civil law regarding marriage, what will be so special about the word “two.” Polygamy and triads of various sexes will be the next push for ‘acceptance.’
As you say, it is all to attack the power of the family which is the bedrock of civilization.
Time for the total weirdoes to come out. How about incest? I want to marry my brother, we are too old to have children, so why not? We are two consenting adults and we love each other, isn’t that the argument?