Wilfrid Laurier, Mackenzie King, Louis Saint Laurent, go pretty far back.  Even Lester was over 60 years ago.  And it certainly isn't in the spirit of justifying atrocities.  It is in the interests of figuring out how things happened so they don't happen again, which is the main reason for studying history.

The gentlemen in the list made mistakes, as we all do -- some of them more than others.  But to characterize them as racists is unfair and inaccurate.

If you want to put the lens of the 21st century on a time when women didn't have the right to vote (Laurier), or the US practiced segregation (King, St Laurent, Pearson) that is your prerogative, but in my opinion it won't give you an accurate view of historical events.