As a general rule, I am a very liberal person (especially on issues race, health care and poverty), however, I think SP makes a very valid point.
Granted, take what I say with a grain of salt, as both my parents were immigrants.
The recent terrorist arrests in Canada are a prime example of what SP is talking about. Canada has been the pinnacle of tolerance and has a EXTREMELY LIBERAL immigration policy, with a good majority of new immigrants (last 20 years or so), coming from India, Pakistan and Sri Lanka.
Without doubt, among these nations there are many fine individuals, however, there are also many with nothing but evil on their minds.
Often, many left leaning people will say something akin to this... "well the US got what it deserved because it did x, y, z (not trying to make this about the US, just needed the example)".
However, what we learned from the recent Canadian arrests, is that it really doesn't matter what the host nation does or does not do with a good portion of Muslims. Canada, abstained from the Iraq war and still (as a whole) does not support the war. They have troops in Afghanistan, but they are there for "peace keeping" not fighting.
By in large, Canada has long held the tradition of "peace keeping" over policing. It has been mixing bowl vs. melting pot and multiculturalism over assimilation.
And for what? Where has it gotten them? I think (realistically) it is probably only a matter of time before Canada has a terrorist attack on it soil. I think that will be the logical consequence of a on overly liberal policy on immigration. In fact, there are already towns in and around Toronto, which probably have a HUGE Islamic majority. A city like Brampton (nicknamed Bramladesh) is probably 50% Muslim and growing fast.
Canada has fashioned itself as the model for tolerance and acceptance. When the latest 19 arrested were caught with enought bomb making material to bring down the CN tower, where was their tolerance an acceptance? In that regard, I'm inclined to agree with SP.