Call me naive

I'm going to go ahead and ask: what, what, is so threatening to hetero married people about gay marriage? Same-sex marriages are already illegal in Florida. But in November, we're going to have the opportunity to vote on a constitutional amendment that would ban same-sex marriages. Wait, what? If there's already a law against it, why is a constitutional amendment necessary? Oh, I get it: so it's harder to overturn than a measly law. I ask again: what is so threatening about it? Why are so many people so vehemently in favor of keeping a group of people from realizing one of society's most timeless rites? Proponents of gay-marriage bans claim that gay marriage would undermine the institution of marriage. "If marriage can mean anything, marriage means nothing," says John Stemberger, chairman of Yes2Marriage. Uh... how is that, exactly? Maybe I'm naive, but I don't understand how my marriage-- or the institution of marriage-- is in any way undermined by gay marriage. Can someone explain it to me? Because I just don't get it.