Yet they claimed there'd be no slippery slope after homosexual marriage, and wrote it off as hysteria among the "homophobes".

Bullshit.
Every pervert in the world is now going to get in line to demand their own particular freak-marriage. Now you've got the poly marriage lobby piping up. How long before the incest crowd wants their marriage licenses? Or Little Bo Peep wants to marry her sheep?
Hell in a handbasket.
Thanks liberals, for another great contribution to our social fabric.