First, start with the ideal that new laws are inherently evil, and that current laws should be used and enforced before resorting to new laws (you see this in the gun rights issue -- we don't need new laws).
The government already had the ability to do what it needs to catch terrorists with the current laws and the FISA court, including sealed warrants and very lenient searches and procedures. FISA court is a rubber stamp on whatever the FBI wants to do in regards to terrorists or agents of foreign powers, but it at least conforms to the Bill of Rights.
Enter PATRIOT, which goes further to remove those minor constitutional inconveniences for law enforcement. Among other things, it expanded FISA to apply to ordinary Americans instead of terrorists even though Congress has determined that FISA's limitation of scope to terrorists did not impede the FBI's ability to catch terrorists (duh).
Basically, due to PATRIOT, the government doesn't have to show the constitutionally required probable cause before going on a fishing expedition on any citizen by broadly saying it's related to a terrorism investigation -- with no judicial oversight of such assertion. So far there have been convictions using PATRIOT, but none had anything to do with terrorism. That is evidence that the FBI is willing to make false assertions as to connections with terrorism in order to avoid certain constitutional protections that Americans have been used to for a long time.
True, a police force with absolute power and a citizenry with no rights would create a place very safe from terrorists and criminals, but I wouldn't want to live there.