Those are a lot of questions to unpack.
Any wild animal that is desperately trying to survive old age or serious injury would likely be dangerous to humans as without weapons we are the most helpless critters in the forest/jungle. (Except for pandas, of course. Seriously, google panda videos and ask yourself how these animals actually survive in the wild....) In going through old newspapers, I've run across several articles where tigers, elephants, bears, and wolves were said to hunt/injure humans out of "hate." As Silverback and Huntster state, yes, a wild animal (Bigfoot) is likely to act like other wild animals.
As to the questions about whether certain national parks are dangerous and what specific cases involve, there is no end of information in threads such as the missing 411 thread at
As to what kind of firearm (not necessarily a pistol) to carry in the backwoods, several members of the Forums who have extensive backwoods experience have offered opinions at this thread.
Between the two threads, that's over 50 pages of discussion on most of the substance asked about.
As to the "should people go out and do dumb things?" question, No. They shouldn't. But that didn't stop some guy from camping out with grizzlies because "they were used to him" or a New Jersey hiker from going up in the Adirondacks in shorts and a t-shirt without adequate food, warm clothing, and other survival stuff, and they both died even without help from Bigfoot.