I’m not so sure they’ll be unsuccessful. In the past few years, California has passed so much legislation giving “domestic partnerships” the same rights and benefits of marriage that little difference exists between the two (Federal recognition for tax purposes is the only one I can think of). We are now left with “separate but equal.”
Think about it. Traditional "separate but equal" referred to physical accomodations, physical things, or physical controls, not imagined slights.
Specifically, the government may eventually arrest me for calling a cripple a cripple, instead of normal, but they can't legislate the faux "equilevancy." Well, OK, they can, but so what? Separate but equal does not transfer to words.
The word marriage has been taken; for millenia.