The media and liberals have calling Bush and Ashcroft fascists since the Patriot Act went into effect. You are correct in your assessment that the media/liberals would have raised holy hell if anything along those lines would have gone into effect prior to 9/11.
You're right, even if Bush had a document stating that airline hijackings were planned to fly into buildings during that timeframe, the only way he could have tried to prevent them would have been to implement draconian security in advance of 9/11...and the public would NOT have accepted that. No way. Unfortunately, experiencing the horror of 9/11 or another terrorist attack on US soil was the only way the public ever would tolerate the kind of security that could have prevented it in the first place.
All these liberals calling for Bush's head would have gone positively ballistic if Bush or Ashcroft had proposed Muslim profiling or tweezer searches or email snooping in the absence of 9/11. They would have called Bush a fascist, or maybe compared him to Hitler! Oh, that's right, they did anyway.