Whilst legal action clearly seems beyond the scope of reasonableness or reality, people really do have options: change your flying to WS, PD, BA, AF, AA, UA, DL, KL, or any of the myriad of other carriers that serve Canada. I doubt that AC will care less that it loses you as a customer, but it may make you happier to take some action on your own behalf. Also, you may see that AC's revisions to Aeroplan aren't unreasonable (IMO), once you compare the new programme to what is available at other airlines. Or not. Everyone's different, and will have different needs from an airline's FF programme.