Preventing the career progression of younger pilots, i.e. those not retiring imminently, is also age discrimination, however you look at it.
This is not the case elsewhere though; there doesn't seem to be much of a moral leaning in industries where there is no requirement for a medical or mandatory loss of privileges at a specified cut-off point. I understand that EASA have recently commissioned a study on this very subject and there is some interest among employers for an extension in some specific CAT operations where much of the training and examining expertise is weighted toward the upper end of the age scale.