Conrad: Did Seeger and smothers censor which is to say deny others access to their stages?

That's not what censor means. A private individual is under no obligation to make available to all applicants any means they have of disseminating information. You might as well say that if I put a "Vote Republican" sign in my front yard, I am censoring the Democrats unless I also allow them to put a "Vote Democrat" sign in my front yard. The Smothers Brothers are not required to give equal time to all political points of view on their television show, and failing to do so is not "censorship." They don't do anything to stop their political rivals from speaking out on the stage next door. If they had power over all the television shows in the country and imposed a moratorium on whomever they disliked, that would be censorship. But in general "censorship" is something that governments do, not private individuals.