If Sonia Sotomayor, Obama's nominee for the United States Supreme Court, is confirmed this summer, she will be the first Hispanic to serve on the court in the country's history. So obviously, conservatives are panicking.

Sotomayor is a 54-year-old, self-described "Nuyorican", a child of Puerto Rican immigrants who grew up in the Bronx. Her father, a factory worker, died when she was nine; her mother was a nurse who brought up Sonia and her younger brother by herself. Sotomayor didn't speak fluent English until she was 10, yet she went on to Princeton and Yale. Now she may become the first woman of colour on the highest court in the land. So far, so American Dream. Or is it?

Because she spent many years on the board of the Puerto Rican Legal Defence Fund, because one of her most prominent cases involved affirmative action, and because of some remarks she made about her Latina heritage at a university conference in 2001, Sotomayor is being attacked as a "reverse racist" (thanks to talk-show host Rush Limbaugh) and as a "racist" plain and simple (Newt Gingrich).

A former Republican congressman described the Hispanic advocacy group National Council of La Raza as a "Latino KKK", and a writer at the conservative publication the National Review argued that Sotomayor was not fully assimilated because she pronounced her surname with the stress on the last syllable. As I read these things, I wept.

I moved to New York six years ago. I am half-Mexican, half-British, and while growing up in Mexico and England I had no direct experience of racism. Yet suddenly, in America, I was one of a racially abused minority.

Most days, the people I speak to in Spanish are part of an underclass and that's never been true in my life before. If I speak English, people here think I'm posh, like the Queen, and if I speak Spanish, they can't believe how Mexican my accent is. There are millions of bilingual people here, but that particular mix is unusual. And only in America could it be viewed as such a clash of classes.

I've had people tell me not to go to certain places because they are full of Mexicans. On the more politically correct end of the scale, I've been chastised for referring to Latinos who were Mexican as "Mexicans".

Somehow, my nationality has become a dirty word. If you say "Mexican" in America, you are not referring to the citizens of a specific country, you are using a blanket derogatory term for "people who came out of nowhere and took our jobs".

The attacks on Sonia Sotomayor are unconscionable, yet even more worryingly, Obama has been cited as proof that we are now colour blind and therefore anyone who has shown direct support for the racial underdog is too biased to be considered as a Supreme Court justice. In other words, now we've elected Obama, we have a licence to get on with being as racist as we were before. Also, blacks are one thing (they've always been here) but these invaders are a real problem. We needn't worry that Sonia Sotomayor will be judged on the wrong terms: there is a Democratic majority in the Senate and she has many Republican admirers. But what about the rest of the country? In the heady first days of this year, many warned that the word "post-racial" was dangerous; we may already be just where they feared we'd find ourselves.