FYI the law does not force a Rabbi to perform a Same gender wedding. If that were the case a Rabbi could be forced to perform a mixed marriage which they are not.
Also it is not legal to force a Yeshiva or Shul to hold a mixed marriage ceremony.
The issue is if someone in a mixed marriage or same gender wedding would want a Glatt Kosher wedding at say the Waldorf Astoria (An event at at neutral location) . I am sure there have been glatt Kosher affairs involving mixed marriages and I am fairly sure Kosher Bakers have made Cakes saying Mazal Tov to Berel and Christine.
I wouldnt be suprised if there have been Glatt Kosher events for mixed marriages, Jewish Flower stores proving flowers for mixed marriages or Kosher Bakers baking the cake saying Mazal tov to Berel and Christine. It has rarely been an issue before.