Let's assume that higher crime rates are caused by poverty and not by the color of your skin.

Let's say you accept the answer you've received based on your heuristic that black people will statistically commit more crimes.

If a policy was based upon this heuristic, then you would have people living in poverty that would not be subject to the same policy. This is what discrimination is about. Citizens would thus not have the same rights / opportunity.

And the only reason you are accepting this heuristic as "good enough", is because you make the assumption that "you have modelled [enough of] the variables that make up the solution space".

This is not acceptable for policy makers and should be watched for closely in a democracy.