That sucks to hear, I always said that if I gun hunted public land again I would want to hunt there. I hunted it a lot during college and its a great area. I know that these tree huggers tried to buy up all the permits for Crab Orchard a few years back. While they probably ruin a few hunters day, with them walking around they probably kill more deer by pushing them to other hunters than they save.
If they did something like that to me I'd probably follow them back to there car and get a description of the vehicle.