Although I'm not equipped to answer this question myself, I can point you towards a reference that might begin to address the matter of how experiences and memories of WWII and the Holocaust influenced Canadians' perceptions of immigrants, and thereby Canadian immigration policies: Franca Iacovetta's fabulous Gatekeepers: Reshaping Immigrant Lives in Cold War Canada. For a brief rundown of Iacovetta's study, see: https://www.h-net.org/reviews/showrev.php?id=23642