The evidence is still disputed, and the validity is encoded in the tests. Modern IQ tests are adjusted to be robust across multiple trials, that doesn’t prove that intelligence is immutable by a long shot, it is merely a self fulfilling prophecy.

Books such as The Bell Curve are not in and of them self racist. This book in particular makes zero racist claims. However it relies on deeply racist studies as its premise, so if you want to conclude anything from it, that conclusion is racist.

I don’t think every proponent of IQ is racist, however there is a lot of racism embedded in the research, sometimes directly, but most often by association.