Are you suggesting crying children or children who might cry be treated similarly? Should a plane be diverted and the offending family tossed off so light sleepers on transatlantic flights can get their sleep?

Maybe a complaint to AC will get you a few Aeroplan points but it doesn't solve the problem next time. Lecturing parents who are not making the effort to soothe the child might work or it might create a confrontation you would regret. The FAs aren't likely going take up your cause either. Ear plugs, noise cancelling headphones, Zopiclone are my preferred options when cabin noise becomes bothersome.