There are people you're stuck with, right? Whether they are born in Canada or they come to Canada and become citizens, you become stuck with them unless you can denaturalize them legally, and legitimately you should have some proof.
Obviously, if a person has come and is in the process of settling himself or herself permanently in the country, but we find out that the person is an extremely dangerous person because we have this evidence from a reliable ally but can't produce that evidence in an open court, what you're suggesting is that we do nothing in that regard unless we can find evidence that is here, that is available to us, that the person has committed an offence. We have first-hand evidence and we can produce that, and then we can deal with the issue.