While Canada may not be Shangri-La, I don't think any Canadian would ever consider or confuse race for a denied boarding/oversell situation. The flight was overbooked, an annoying situation but common practice amongst the vast majority of North American Carriers, no volunteers found & most regrettable. End of story.
I highly doubt its racism. AC routinely discriminates against award tickets, you get last priority for oversold flights, for which AC provides pathetic compensation, they don't have much motivation for soliciting vols more since their blanket policy of $100 cash or 200 voucher seems universally applied. Transport CAnada recently ruled that they're going to have to change that policy to be more inline with what the US and EU rules that are much more customer friendly.