It is difficult to know if our criteria are too strict. I don't know how to determine what the best balance would be.
How do you determine what the optimum balance is?
How many terrorists should we let in that's going to prove to be optimal? Probably the politics of this suggests zero. How many people who are going to stay on a temporary visa and not go back are we prepared to accept? Inherently, it is a political question, and it's something that you politicians have to come to grips with. It's very tough to find the right answer.
There isn't a technical solution to this question, I'm afraid. You need to come to a judgment about what it is.
My encouragement to you is don't search for zero tolerance. Mistakes are going to be made. There is an optimal quantity of errors.