Laws like this are one reason I joined Americans United For Separation of Church and State. Check 'em out -- they're very politically active in such matters. Their chair, Rev. Barry Lynn, is extremely well-spoken and highly visible in the mass media. They're worth supporting, IMHO.

From ReligiousTolerance.org:

Gallup Organization polls (1937 to 1999) on religious prejudice:

Polls by the Gallup Organization are of particular value because they have asked essentially the same question of American adults for over four decades. One series of questions is typically worded: "If your party nominated a generally well-qualified person for president who happened to be a 'X' would you vote for that person?" "X" is Atheist, Baptist, Black, Catholic, Homosexual, Jewish, Mormon, and Woman. Percentage of unprejudiced adults (those answering "yes") at approximately 20 year intervals have been:

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In 1978, the most discriminated-against characteristic was homosexuality; only about one in four Americans would vote for a well-qualified homosexual. Gays and lesbians have made impressive gains in acceptance. Now, about three in five Americans would consider voting for one.

In 1978, the second most-discriminated against group were Atheists. Only four Americans in ten would vote for a well-qualified Atheist. In 1999, Atheists had made a slight gain; five in ten would vote for one.

Oops on the linky above. It's: Prejudice of Americans Towards Those of Other Faiths.