I've seen such data and won't debate them. But are you drawing the right conclusions? Was there more or less crime in the Jim Crow South?
Less crime as a result of relative homogeneity across race, religion, income, education, health care - which is what we see in Scandanavia - correlates with lower diversity, obviously. Less crime as a result of segregation and institutionalized racism - which we saw (and are likely to see again) in the Jim Crow South - also correlates with lower diversity, obviously.
If your objective is less crime through less diversity, I would suggest achieving that through the Scandanavian approach - not the Jim Crow approach.
Don't get me wrong, some diversity can be bad. Too much diversity in health care - such that some people get Cadillac care and some get little or none - is one example. Too much diversity in wealth - such that we have a few billionaires owning as much as the bottom half of our society, and we have the obscenely rich and the wretched poor in the same country - is another example. Ditto for the great diversity in education. And for the availability of clean air, water and land.
Liberals try tackle the diversity "problem" through leveling and elevating approaches like public education, progressive taxation, Medicare, an aggressive EPA, and so on.
What do conservatives do? We're seeing that now.