What evidence would you want to see. Whatever you think about the beheading videos, what about the videos of them mowing down towns. Why do you think they're fake?
The problem with the conspiracy crew is that they don't know themselves.
See, the government lies all the time and we all know this.
http://en.wikipedia.org/wiki/Nayirah_(testimony)
They lied about Saddam killing babies.
He wasn't.
But its easy to believe that when Saddam is already a dikkhead.
However, the only time we found out was AFTER the fact.
We're really poor at predicting lies...and they often lie about the least obvious things.
So essentially, these guys are trying to predict the next "lie" so they can pretend to be ahead of the curve, when in actuality, they really don't know so at best all they can do is to pretend that the opposite of what their government says is true in an attempt to "stay ahead of the curve"
Its like a scorned woman thinking the worst of all future men.