David S- I think by interracial she means between a white person and a black person. There would be no issur for a white Jew to marry a black Jew, so long as both are Jewish al pi halacha.
SJS- it is important to protest because when we allow these people to marry, we are, in effect, saying that those kinds of relationships are normal and acceptable. I know many frum people who struggle with a very strong yetzer hara to commit toeiva actions,they know it is wrong and they are always trying not to succumb (sometimes they do succumb, but they try to do tshuva for it and do what they can not to do it again) and such people deserve our consideration and support and any help we can offer in their fight against the yetzer; but the people pushing for marriage are not interested, they want our society to accept their lifestyle as normal, which is something no God-fearing individual can do.
This extends beyond marriage, and into “civil unions” too. What is marriage in the USA anyway, other than a piece of paper stating that you are married? Civil unions and domestic partnerships are basically marriage without the name. A rose by any other name…
Lastly, about minorities: the term minority, as I understand it, deals with religion and/or ethnicity. Blacks, Asians, and Hispanics are minorities; Jews, Muslims, and Hindus are minorities. These groups deserve certain basic rights- the right to practice their religion (so long as they’re not killing people of other religions…), the right not to be discriminated against at work, or in public places, etc. Practicing a deviant lifestyle does not make you a “minority” who needs protection! A white gay male, so long as he doesn’t flaunt it, or try to force his way on everyone, will probably have no problem finding a job, will likely not get beaten up in the street, and will probably not be excluded from parks or country clubs. A black gay male may need to rely on laws to protect him from discrimination at work or other places not because he’s gay but because he’s black; he is the minority because of his ethnicity, not his lifestyle. So, I don’t feel we are denying a “minority” anything in this case. Hope this helps.