While you may very well be correct that this was never performed in C, (it's in Bb on the album), I disagree that it should be taken down for that reason. I found myself wondering how I ended up in C, and I checked the Grateful Dead Anthology vol I, and that was the key it was presented in there, so at least that answers that.
Regardless....learning to transpose is a practice that has immeasurable benefits. Although the song is in a different key, it is not incorrect. And, btw, no one ever said that for this song or any other, that you have to do it in the key they did it. People get too hung up on that stuff imo. They changed keys on songs when it made sense for them to do so. It doesn't make it wrong.