[dragonwriter]

> You might as well ban giving maths tests.

No one banned giving any kind of test. What the case at issue found illegal was using a test that had a discriminatory effect when the employer could not demonstrate that the test at issue was "a reasonable measure of job performance", based on the Civil Rights Act of 1964, wherein Congress banned job discrimination on race and placed the burden of proof on employers to demonstrate that practices with disparate impact were reasonably job related.

> I think you'd agree that IQ does not discriminate based on race at all, it discriminates based on class.

Tests don't discriminate, people do. An employer who has an overt policy of racial discrimination, who replaces that policy on the day the Civil Rights Act of 1964 goes into effect with an IQ test requirement covering the same jobs that were previously covered by the overt discrimination policy, where results on the test in question both has disparate racial results and have no demonstrable tie to performance in the jobs covered, well, its not hard at all to see that as the employer (not the test) discriminating on race, using the best tool for that purpose that they think they can get away with.