Just reading this makes me angry....first of all, what business did they have pulling up right behind you, when they could see you were fishing that stretch? Secondly, my answer to "I'm a taxpayer, etc etc" would be to say that I'm a taxpayer too, and you're messing up my share of the park (at that given period in time). You handled it far better than I would have - I know my temper would have gotten the better of me. The worst thing is, they were supposedly there to fish - they don't even have the excuse of being just a typical dumb tourist.
We fished Straight Fork on Sunday, and while it is a pretty stream, it does have a lot of litter. I found a can in the stream, and one of my daughters found a case of Bud, with a few cans left in it. I imagine a lot of that stuff is from teenagers driving up there from Cherokee - again, I don't think it's fishermen doing that.