Who was the KKK protecting the townspeople from?

Although this is ostensibly about the KKK, in the early 50s you can count on films about this sort of anti-others fear-mongering theme being about McCarthyism.

A brief recap of US history, which you might very well know better than I (not being a US resident since age 5): Racism in the United States wasn't only a black-white issue, historically. By the time the Native Americans had been effectively silenced, and slaves supposedly freed, in the mid 19th Century, most urban racism concerned the newly settling Irish, then the Italians, then European Jews, Germans, Polish, Greeks and every other of dozens of nationalities coming in through Ellis Island. When this movie was made in 1950, popular culture had only just tackled anti-semitism three years before in Gentleman's Agreement, and also in 1950 came pro-Native American westerns from major studios, Devil's Doorway and Broken Arrow. Storm Warning was still a ground-breaking film in its day because pro-African American sentiment by the majority of the population was still a few years away from full flourish, and major businesses like the Hollywood studios were concerned primarily (but not solely) with butts on seats. Given the lag time of generations to get over putting parochial interests first, it is no surprise that Hollywood wasn't tackled about anti-Italian "bias" in its gangster films until the mid-1930s and for decades there was still palpable clannishness in Hollywood staffers like the Irish cabal of actors at Warner Bros (as one example).

I am always amazed at the naivety of some posters here, who look at the 'distant' past with no understanding of it, and with the 'eyes' and sensibilities of today; using your logic, you could say the Founding Fathers 'wimped out' on racism, as did the black slave-sellers in Africa who sold black slaves for much more than a century. You do know, I hope, that racism/slavery still exists in the world today -- in MANY places. There, they're still 'wimping out', with NO chance of films like this showing anything about such in those places -- not unless you want to risk being beheaded, or suffering some other awful punishment, for doing so.

"Outsiders" is a deliberately vague term. If the film were made today, there would be no question that it's black people that the KKK is against. It would not be so coded that it's almost not there as it is in this film, so as to appease the southern market.