He was a liar whose grandiose and narcissistic tales ended up getting two grizzlies killed for NO GOOD REASON.
http://www.rottentomatoes.com/m/grizzly_man/about.php
EXCERPT
"Adding more fuel to the controversy is the fact that aspects of Treadwell's life remained shrouded in mystery until his death. He lied about his background even to his close friends, claiming to be Australian when in fact he was from a middle-class family in suburban New York. He had a history of serious drug and alcohol problems and had had several run-ins with the law before devoting his life to bears, which he credited with turning his life around."
END EXCERPT
Grizzlies are wild animals, not an excuse to grandstand or a means of gaining celebrity. Treadwell, who lied about his past and who may have fabricated much of his celebrated "study" of grizzlies, caused more harm to these animals than any hunter could have done with a gun. Rather than educate the public about the true nature and majesty of grizzlies, Treadwell created an environment where people would deliberately expose themselves to these magnificent and dangerous creatures, resulting in death for both people and grizzlies.
All very true. But, being a bit of a Werner Herzog fan, I have to say that the documentary doesn't glorify Treadwell at all. In fact it pretty much unveils Treadwell as a tragic lunatic.