re: Why do dem-governed cities have the highest crime & murder rates?

Endemic crime is largely the result of black market economic activity. Those who rely on entitlement programs often risk losing those entitlements if they attempt to make money legally. Their only avenue for economic advancement that doesn't involve losing their benefits is thus to operate on the black market (counterfeit goods, selling contraband, all-cash businesses, etc). This shields their earnings from taxes and from triggering the welfare cliff. Black markets are governed by force since there is no legal system to resolve disputes. Those on cradle to grave entitlements overwhelmingly vote democrat. Thus, places with high concentrations of that part of the democrat voting block often have high rates of crime.