>Pensions and taxes are the main reasons governments want immigrants 

Except, if they can't get jobs, both of these don't happen. 

>As mentioned elsewhere, there are a lot of jobs that 3rd+ generation people won’t do, at least for minimum wage.

For sure. And, a lot of second and third generations, are integrated, and are highly educated, but still carry a work ethic. Fourth generation, not so much...

>The reasons against almost always come down to racism and “replacement” fears.

This is the current argument for sure. 

>It’s funny how in Canada we never faced any suspicion despite our obviously non Canadian accent. Strange huh?

Not sure how long you have been there, but has it changed over time?