This…that’s…I’m speechless. This is fantastic, is what it is. Just dead-nuts fantastic. Good show, sir, very good show indeed.
You could always bite your thumb at them, like in Shakespeare. 
I’ve actually done that at protesters a couple of times.
. . . all while making out with your nearest friend of the same sex.
I’d be tempted to make my own sign and stand next to those people holding the latter sign. My sign would read “and a goat”.
I like and support traditional marriages… I’d be some kinda serious hypocrite if I didn’t. After all, my wife and I have one. 
That said, I support the right of anyone to bind their lives to another in a lasting public commitment expressing their mutual love and devotion. Their commitment to each other has zero impact on mine to my wife. Why should I deny others the joy, challenges, trials, comfort, love, and triumphs we’ve experiened together?
Generally, I find protestors of that sort to be massively irritating.
- They’ve utterly lost the plot - Marriage is a commericial (old-school) or social (more recently) contract between two people and, maybe (if you’re really traditional) their families. Where does gender actually enter into that?
- NO ONE is messing with their relationships, and
- They fuck up my commute!
Well, given your leanings, would you be in favour of polyandrous gay marriage?