Terrorists aren't much like criminals. For a start, they're ideologically motivated. And that's the argument for why we as a society, need to treat terrorists differently than criminals in the first place.
There's only a very, very few terrorists, even when the US government has done its level best to create as many as possible. I doubt we can take a quantitative argument like yours and get decent results.
The term "bad guys" is much broader than just terrorist. Feel free to substitute "drug smugglers", "human traffickers", "members of organized crime groups", "militant extremists", or, yes, even "terrorists". Nor did I make any argument as to how to handle any of them. The point is that you don't have to be smart to cause harm. The smart ones were presumably harder to track beforehand; the not-so-smart ones are likely a lot smarter now.
