Upwards of 20 members from the Revolution Club of Chicago -- who are self-described commies -- staged a protest Saturday outside of Jason's concert near Chicago, where they were marching, chanting and flag burning. Yes, they set Old Glory ablaze -- a couple times, in fact.

Several of them specifically called out JA, saying they weren't afraid to try anything anywhere -- going on to call him a "fascist piece of s***." One guy who was on a megaphone also shouted ... "We will try that in a big city. And, we will try it right in front of your concert."

The demonstration seemed to be both anti-Jason, but also ... anti-America. One chant included the phrase -- "F*** the U.S. and all its might," among other derogatory zings.

Eventually, several police officers showed up and told them to scram, announcing that their gathering had become unlawful and that they were disturbing the peace. It sounds like the group dispersed shortly thereafter without further incident ... so no arrests here.

The controversy from Jason's hit song, "Try That In a Small Town," clearly continues to reverberate across the country -- even all these weeks later. And yet, he's still going to a ton of major cities and drawing a crowd.