NASA is justly criticized for tending to deal with a select group of scientists, but that's more a factor of how science works than of governmental intervention or suppression. And many critics who claim NASA is withholding information are predisposed to believe that, and so innocent mistakes or inaccuracies are sometimes "spun" to suggest malfeasance. The Enterprise Mission is notorious for doing this.

As far as dealing with conspiracy theorists, NASA is in a lose-lose situation. If they remain silent, conspiracists can postulate any reason they wish for the silence and for what's being "hidden". If NASA offers refutations, the conspiracists either dismiss them as propaganda, twist them to suit their needs, or refine their conclusions ad hoc to accommodate them.

NASA's response is mostly proper. Since the hoax theorists offer only conjecture and very little in the way of proof, there is no need to provide an elaborate response to a case which has not yet been made. Conspiracists complain that NASA does not address their arguments, oblivious to the fact that NASA has indeed provided mountains upon mountains of evidence in favor of its own competing conclusion. The conspiracists provide no evidence, but want NASA to grant them credibility by acknowledging their conjecture.