You think all of those folks are just making this up?
I don't know for sure, but none of us have seen proof that Osama Bin Laden was killed.
Many of these (otherwise good honest) people who've seen proof probably aren't very objective considering their position and interests, and probably don't even know what they're looking at.
I certainly don't trust Al Qaeda, Obama, CIA, parts of our Military, or the Bin Laden family who supposedly cut ties with Osama.