yuubah,
I'm sorry, but this is beyond outrageous. It is beyond unprofessional.
As many here know, I fly YVR-NRT on a regular basis. There have been infants and children in J cabin on many occasions. Infants cry. That's life. I am sure your sister and family did their best to comfort their child.
In no way would I EVER give up my seat in a very expensive cabin to move to economy or elsewhere.
I realize this is hindsight as we were not there with you but, I would have taken the name of that flight attendant. I would have spoken to the SD (unless they were the same person) and taken their name.
Then I would have recorded audio or video conversation on my phone. Others here may say that is a breach of privacy. This crew member's behaviour was far worse. IMO.
Who in their right mind would force PAID BUSINESS CLASS passengers to move because their child was crying.
If going to the media ensures that Air Canada provides full compensation for denying your sister and her family the seats they paid for, then do it.
(and yes, I do get the "position" that AC got them to their destination. Of course they did, but that is not the point here....and a 5% or 15% promo code will not solve the problem - nor prevent this from happening to someone else.)