I'm going to be cynical here and suggest that there was no emotion involved for the legislators themselves - they knew the consequences from the beginning. They wait for constituents to become emotional and irrational to push through shitty legislation.
You're assuming that the power-grab of government is all-encompassing, and that all parties collude equally. I doubt this is true.
Even congressmen are human, and at least some were caught up in the emotion.
Cynically (and I expect downvotes) I even imagine Bush caught up emotionally, as old-school Cold War vets Cheney and Rumsfeld finally saw a chance to pounce on popular fervor to increase executive power. Perhaps I'm wrong, but history seems on my side.
If you consider the account of what happened surrounding the passing of the post-9/11 legislation as given here[0] factual, it was very much transported on emotion.
Sure, the original concept wasn't new, but I'm fairly certain the emotional landscape at the time was intentionally used as a vehicle to pass these kinds of laws.
The saddest part is that many people who did pay attention at the time were fully aware of where this would go and were criticised or ridiculed at the time. My first thought upon learning of the PATRIOT Act was that it's a creepy name for a bill that permanently erodes civil rights and protections, but apparently most people thought it was okay because A) it has a name you can't possibly argue with (being considered un-patriotic in the aftermath of 9/11 would have been outrageous) and B) it's only for dealing with terrorism anyway.
Kinda reminds me of the Internet censorship bill our politicians in Germany tried to pass some years ago. It was only to be used to restrict access to child pornography, of course. Because if there's one thing that's easier to rally people against than terrorism, it's child abuse. And who can argue with combating child abuse?
