Long-time reader(s) will have noticed that I have stalled on my promised Singh blogathon. But I would like to point you to Thomas Sowell pointing out the tension between a generous immigration policy and affirmative action. Of course, he's against either, but without endorsing his position, I have to agree that you can't reasonably ask the native population to accept both.
Immigration is only defensible if it benefits both the immigrants and the existing community.* And it can't do that if the existing community is denied legal rights that the immigrants will get as a result of their skin colour.
Caveats: Totally separate issues arise in relation to aboriginal people. And, under the cover of bilingualism, the federal government will inevitably practice affirmative action in favour of francophones. I can't say I'm against such things in principle. Ethnicity is a reality, and I do not believe that the results of the free market or "meritocratic" competition are intrinsically more moral than politically-based ethnic allocation. Every polity with more than one ethnic group must have some of the latter.
But I can't defend the interaction of such policies with voluntary immigration. Anyone willing to do so is free to use the comment box.
*I recognize that you could, in principle, deny this. In fact, if you are a utilitarian, you are committed to denying it. But I think that's a problem for utilitarianism at least as a decision-making rule for national politicians. I might get into this more if I get annoyed with Ignatieff again.