There will always be room for abuse. There will never be any "bright line" to protect us from bad people. Someone says "we're a nation of laws, not men." That's not totally true, for every democratic republic must rely to some extent on the good faith, acts, and intentions of its citizens and officials. I'd say that it's worked pretty well so far.
Yeah, but sometimes we need to hold the line or at the very least create as much friction as possible so things don't get carried away. Terrorism has been around forever and it's not going to just go away, so anything we give up it's likely permanent. The government just wants to do what ever it takes to get the job done, problem is we and future generations have to live with it, so choose carefully. I don't know if a big intrusive government which gives the illusion of safety is the right way.