No, they are not entirely meaningless, as you can demonstrate clearly the substantial effect they have by correcting for poverty, education etc. in the crime number and comparing the uncorrected / corrected results to see the effect they have.

When you then further break that data down by race, the purported intelligence differences and testosterone differences you claim either have no effect, are non-existing, or they have fallen away as a side effect of removing the other confounding factors, as eradicating socio-economic factors mostly erases racial differences in crime rate.

If they are real, have an effect, but fall away when correcting for other factors, then that suggests that these effects themselves are caused by the same confounding factors, and are not down to ethnicity after all.

E.g. it'd not be surprising at all if IQ test results in a poor, uneducated subset of a population where parents have less resources to invest in their childrens wellbeing, and where the chance of malnutrition is higher, are worse than in wealthier parts of a population. But the obvious place to look for causes are in the many known causes of low performance of IQ tests, several of which co-occur fairly frequently with poverty.

Any study that tries to pin such a difference on ethnicity is outright trash if it has not controlled very carefully for a rather extensive set of other potential factors. Including directly controlling for factors such as nutritional differences.

Another part of the reason for the outrage at claims like this, is that trying to pin down "black Americans" as an ethnic group is hopelessly flawed from the outset, given that "black Americans" genetically range from mostly European descent to entirely African descent, but with the vast majority being substantially mixed, and that discourse on that in the US is largely dictated by a combination of racism and cultural factors that one one hand makes it impossible for most mixed people to "pass as white" even if they have far more European than African ancestry, and on the other hand makes it culturally hard for a mixed person to identify as white without being considered a sell-out by the black community.

E.g. Obama is no more black than he is white, yet he is automatically considered black in the US by pretty much everyone, and would face flack from both "sides" if he were to try to describe himself as white.

Because racial designation is mostly a social construct that is largely down to peoples immediate knowledge of their ancestry, skin colour and social considerations rather than genetics (I'm reminded of the difference with the Portuguese, who during their colonial era and a higher willingness to openly intermix with the local populations had an intricate system of something like 12 different distinctions of levels between white and black that affected your social standing, which anyone who knows people with mixed children knows would be largely "luck of the draw"), it is highly geared towards being easy to manipulate (don't get the numbers you like? redefine "black" to find a definition that moves the delineation between groups in your study, and odds are you can find some dividing line that fits your agenda) which in itself makes any numbers suspect.

But even with a researcher without an agenda, without extensive genetic testing, result would at best tell you that people who self report as black fall in one group, and everyone else fall in another. Of course then you don't know if - assuming you had in fact isolated a trait that actually has a genetic component - the trait you are reporting on is actually a result of a genetic trait tied to "being black", or if it stems from the European intermixing into the "black" population that just isn't significant enough to affect the overall white population the same way.

I've yet to see anyone come up with research that claims such differences that does not fall flat on its face either by failing to address sufficient confounding factors, or by failing to at the very least discuss the considerations of how it ethnically delineated the population and why.