I think Airdale has made an excellent point. Perhaps it's not that the government is trying to cover up the existence of Bigfoot, on a grand scale, but rather they are unwilling to confirm the existence of Bigfoot and discourage any talk or comments from public officials, because it's not been proven to exist.
Using an example from Airdale's post; if a forest ranger or rangers, observe Bigfoot in the area, would they be encouraged to speak openly about this sighting? The answer is no; they would have to keep quiet because they would be perceived or judged as being crazy.
I'm a partner in a privately owned company and even though my partners and associates know that I have an interest in Bigfoot, they also know I would not discuss this interest in front of clients. Simply because there's a stigma that's associated with people that believe in Bigfoot. The government is the same as the company I work for. They don't want the stigma of being associated with this subject matter as it does not "officially" exist.
This holds true for many other things, aside from BF, such as UFO's, ghosts, etc. I may not believe in ghosts but who am I to judge?
Imagine how the world would look upon us if the FBI announced that it believed in the existence of ghosts, trolls and Chupacabras? I'm sure some special interest groups would think this was great but most people would instantly lose confidence in the FBI. Bigfoot, from the public's perspective is really no different.
The bottom line is that government employees, agencies or officials cannot discuss topics such as Bigfoot without leaving themselves open to ridicule or scorn. They have to be seen as above board in all ways. Until BF is acknowledged by the government, he won't officially exist. I have no doubt that cops, rangers, soldiers and all sorts of government officials have seen these creatures. However, the agencies they work for will not officially acknowledge these sightings for the same reason I stated earlier
Therefor, the government is not trying to cover up the existence of Bigfoot, they are just stating that he has not been proven to exist. All public servants will "officially" have to follow the same position. There's a significant difference, in my mind, between this and a cover up.
Again, there's no logical reason, I'm aware of, for the government actively trying to stop us from proving the existence of Bigfoot. Otherwise our ability to hunt, hike and camp in national forests would be restricted. TV shows like finding Bigfoot, would not exist. This website would not exist.
This is really a matter of official denial and not a policy of trying to keep us from knowing. After all, it really is a bit late for a cover up; don't you think?
Whenever I hear "cover up" as a reason for why proof cannot be produced or made available, as it pertains to Bigfoot, I immediately question the claim or testimony.