The steps taken by the Bush administration (and Congress) post-9/11 to protect the U.S. from further attacks sent the Left into apoplectic fits, and this was after the fact of 3000 citizens dying on that day. If he had initiated even one-tenth of those policies based on nothing more substantial than "Bin Laden determined to attack the U.S." in an intel briefing, can you imagine how hysterical they would have become?
On top of that, every day after 9/11 that intel on further possible terrorist threats were made public they ridiculed the idea and mocked it with snark about "Terra! Terra! Terra! Fear! Fear! Fear!" and downplayed it all. Even their pig-god that they worship, Michael Moore, infamously claimed, "There is no terrorist threat!", and they clamored for our intelligence networks to be dismantled.
That is enough for any thinking human being to dismiss out of hand any and all opinions these fartsuckers have on the matter.