Under certain circumstances, Ibbitson's point would be valid. Unfortunately those are not the circumstances in Canada today, where our immigration system is largely based on the needs of the would be immigrants as opposed to being based on the needs  of the country as a whole. 
A very large percentage of today's immigrants lack the skills and knowledge to make their lives in Canada a success for both themselves and for the country. Furthermore, many of those that are qualified have an intent to use this country as a safe and kind base in which to park their families while they continue to run businesses in their original countries. They are a massive drag on our social systems which very clearly cannot cope with the desperate needs of many unfortunate people who already live here. 
Immigration should indeed be a net benefit, but under our current system and policy it is simply disingenuous to pretend that it is so.