Ockham's Razor: "All other things being equal, the simplest solution is the best."
Heinlein's Razor: "Do not attribute to malice what could be more easily explained by stupidity"

Ockham's Razor != Heinlein Razor

It's often called Hanlon's razor because he quoted that in a 1980 book, but it was originally used by Robert Heinlein in his 1941 short story "Logic of Empire".

http://en.wikipedia.org/wiki/Hanlon's_razor

Heinlein's Razor: Never attribute to malice that which can adequately be explained by stupidity. I somewhat agree with you in the WW2 example, because there's sufficient evidence to show that Roosevelt wanted us to join the war (because we needed to join the war). But the Lusitania disaster was completely due to stupidity, and the Gulf of Tonkin incident was due to the trigger-happy captain of the USS Maddox, not some giant conspiracy to throw us into a war.

Additionally, I think you assume too much intelligence and foresight on the part of the Bush Administration with regards to the WMD information.

The point is you're innocent until proven guilty. Think about the Duke Lacrosse team; their Lacrosse season was disbanded for a year and their names dragged through the mud, and in the end they were innocent. They weren't angels by any means, but they did not rape someone. Reputation is hard to gain back.