Interesting. I did not know that.
During the Civil War the Red Legs were filthy ruffians who reveled in the blood of their many victims and fought without honor.
I spit on their name.
Of course, I derive this opinion solely from the movie in question.
Prior to, and during, the War Between the States (that’s the Civil War to yankees) Kansans would put on red leggings and raid into Missouri.
They claimed the leggings were the uniform that marked them as an official militia, but they were known even in Kansas as vigilantes.
For generations a native of Missouri calling a Kansan a Red Leg was worse than calling them a Godless Something Or Other.
The Kansas Missouri war was some of the most brutal fighting because it was between groups of civilians loosely formed into militias and vigilante groups.
Missouri took the worst of it because while there was little in the way of official Confederate forces there, Kansas had a detachment of Union cavalry that kept most of the fighting in Missouri.
The great exception was when Lawrence, Kansas was raided by Quantril in 1863.
https://en.m.wikipedia.org/wiki/Lawrence_massacre