If you look to Hollywood for a good history lesson, more often than not you'll end up more mixed up than before you started! This is particularly true in older films but still happens a lot today. Much of this is because film studio executives are NOT history teachers and their concern is selling tickets and making money.
I mention this because it's very important as you watch "Bad Men of Missour" that you understand that the movie is mostly fiction and makes evil criminals heroes! According to this film and many others, following the US Civil War, evil Northerners descended on the newly conquered South in order to exploit and humiliate them. So, in these movies, to counter these evil 'Carpetbaggers', good vigilantes kicked them out and restored law and order....at least that's how it is in the films. So who were these 'nice' vigilantes' according to Hollywood? Well, they'd either be career criminals (such as the Younger and James brothers) or the KKK!! Talk about an insane view of history!!
The story begins just at the close of the Civil War. Southern troops are planning on returning home. But when Cole Younger (Dennis Morgan) returns to his beloved Missouri, he finds evil Yankees there...robbing and killing and exploiting his people. So, he and his friends have no choice but to take the law into their own hands. This movie shows their exploits and the 'nice' stuff the Younger gang did.
The problems with the story are many. But hte most obvious is that the Youngers (as well as their friends, the James brothers) were bank robbers and murdered people. They were NOT Robin Hoods but robbing hoods.
So, if you divorce this film completely from fact and just look at it as fiction, is it worth seeing? Yes...provided you don't internalize its awful message. Morgan and the rest are very good actors and the baddies (Walter Catlett, Howard De Silva and Victor Jory) were wonderfully hateful. The story, incidentally, is pretty similar to most B-westerns of the era but with the Carpetbagger and Younger brothers elements added. Without this, the film would have been more enjoyable and honest.