Interestingly, rural areas often have higher crime rates than urban areas.

I tried finding a list of crime rates by county, but most of the lists I found were listing crime rate by city, not by county. This article is the closest thing I could find, although it lists counties by how dangerous they are (including non-crime health threats). But the authors did include crime statistics in their ranking, and they explain their methodology.

Admittedly, several of the counties on that list lean democratic. I started looking into the voting results of recent elections for each county, but it was more effort than I'm really wiling to put into a reddit comment. I think it's worth noting that those counties also have higher poverty rates. I'm sure Arcons will disagree with me on this, but I would say that poverty rates are a better predictor of crime rates than party affiliation or race (I have a funny feeling that the commenter was really saying that people of color are more likely to commit crimes, and are also more likely to vote democrat). Which isn't to say that poor people are all criminals, obviously. But people living in poverty have fewer economic options, and criminal activity is often more profitable than the shitty jobs people can get in a depressed economy. People in poor areas also have less access to education, student extra curricular and after school programs, good nutrition, mental health care, family planning tools, and other social supports that make people less likely to turn to crime. And poor towns tend to have less resources to invest in police.

So I'm not sure that I can say that the linked statement is totally inaccurate, but I definitely think the spirit of the statement is wrong. Yes, people living in impoverished areas with high crime may be more likely to vote for Democrats. But that isn't really surprising, when you consider that the Republican message is often "It's your fault that you're poor, you should bootstrap harder. I'll help bring jobs to your area by reducing the corporate tax rate, so that big companies will come in and hire people to work shitty minimum wage jobs. And I'm going to pay for it by cutting all the social programs that your family relies on to survive, and also all the education and after school programs that you were hoping would help keep your kid off the street and give him a chance at a better future. Oh and we're also going to save money by switching the municipal water source over to this polluted river, so you should probably buy a Brita filter or something."