It's a mess because ACPA and many of our pilots are incapable of recognizing inexorably changing conditions and adapting to them. Not a good characteristic for airline pilots in my opinion, but one that Air Canada seems overly inflicted with nevertheless.
Your opinion that age discrimination is not as serious as the other types is shared by our union and many of our pilots as well. The law however does not agree with you, and that is what counts here.
You are right though that every pilot at Air Canada will (hopefully) turn 60 at some point. One would think they wouldn't want to be discriminated against when they do reach that age. I know I don't want to be.