I guess it depends on what you mean by actionable. If by actionable, you mean "changing my vote won't necessarily have an impact on the murder rate", I'd very much agree with you. However, I'd say it's actionable as in, "I should stop accepting and/or repeating a false narrative", I think that action is warranted.

Sure, if you could find data showing that when you look at the city level, that there was a distinct rise in the murder rate based on partisan leadership that differed from state-level trends, you could maybe make that case. However, it seems incredibly implausible that states with larger cities, cities more often lead by Democrats, and with a larger portion of their population in those cities, would have a lower murder rate and a lower increase in their murder rate, yet the larger trend of increased murders would be due to disproportionate increases in murder in cities lead by Democrats. At the very least, it would require that States that broadly vote Democrat would in aggregate have dramatically lower murders and increases in murders, which would also be in conflict with the partisan narrative.

Confirmation bias tends to manifest as a desire for more in-depth analysis for statements that violate one's expectations, but the rational case here is that the prevailing narrative needs far more in-depth analysis to deserve any kind of support.