What I find odd (and annoying) is that lately left wing politicians in both Canada and the US have started calling people against ILLEGAL immigration racist. Until recently everyone was against breaking the law.
It's all a matter of votes.
Back in the 60s and 70s most left-wing parties in Europe (not sure about the US and Canada) were against immigration, legal or illegal, because it would steal precious jobs from the locals. However that soon became the opposite when it became clear the virulent rhetoric against immigration could be turned against the right-wing by attracting those immigrant votes, and promising even more immigration-friendly politics. It's a positive feedback loop that is beneficial for both the left and the immigrants except in the rare occasion immigrants would vote en masse against socially liberal politics such as California's proposition 8.
It's sort of a risky proposition since a lot of local voters tend to become more disgruntled in turn and vote for right-wing reactionaries who promise to reverse the situation: like California back in the 90s passing bills making English the only official language, building border fences etc. but then it was too late already, demographically speaking, and the state quickly shifted back to the left-wing. Canada and the whole US could follow the same path soon, while in Europe the situation is more favorable to the anti-immigration parties on demographic grounds (and moral grounds as well, since Europe it's, uh, not land stolen from the indigenous peoples).
OT - the rationale and arguments of both sides were so poor that they could very well be US presidents at this rate :P