Yeah, I feel you.
My wife and I have raised our children in a very progressive, accepting environment, and so far they have turned out to be just exactly the kind of people I've always hoped they would be. But that's definitely not true of our extended family. There's never been any doubt whatsoever about where they stand on these types of issues (just slightly to the left of the Nazi party), and they NEVER miss an opportunity to tell you just exactly what their take on it is.
Almost as if they've known something was "off" with me since I was a child and they're baiting me or something, I dunno. It's frustrating as all get out though. Kudos for keeping the peace. Even though it might not have been the "rightest" thing to do, I can understand that it may have been the socially necessary thing to do.
I've been in that situation before too many times. Who wants to be the family that descends into a shouting match at the outback steakhouse on a Sunday afternoon? And usually it's just one or two loudmouths at the table, and really do you want to do this with grandma there she's like 90, she doesn't even know what day it is!
So you damn near bite a hole in your tounge, while your kids (whom you've told to stand up for what's right their entire lives) watch you fold.
It sucks! But I totally get it. Hang in there. There will eventually be a time and place that is right for this confrontation, and you will totally get to righteously unleash!