Based on a British survey of 100,000 Muslims, where 40% favored Sharia law under "some circumstances" I would estimate that at least 500,000 Canadians would not pass, but that is irrelevant.

Because the issue is the future, not the past.

As an analogy, if a particular traffic intersection was found to have contributed to an increase in accidents, I suppose you would be in favor of leaving it as is?