The version that I heard was that during a concert, right before singing a patriotic song, he said he was going to do so, so if there were any witnesses in the audience, they could leave if they wish for that one song.
I DID go to a John Denver concert, and no, he never brought witnesses up at all. But, that was just one concert.
We all have been guilty of saying something at some point that I am sure we wish we didn't at a later time. So even if he did do what he is accused of, I will not let that change my thought of him as an entertainer.
When we think about it, what are the most sensitive subjects to a person? Religion, and politics. Well, the witnesses belong to a radical cultish religion, and thus refuse to have anything to do with politics. To many people, this is just unheard of. So I don't think it is unreasonable for someone, even Denver, to not understand, and say something about it.
As far as the Carson show, I can't help but think that all shows are taped somewhere, and if this did happen, there will be proof. As shown before, Denver was on the Tonight Show many, many times. I find it hard to believe that he would have been kicked off, and then returned. I heard about this rumour well before his last appearance in 1990.