It has been more than two decades since I have flown with a baby of my own and, of course, mine were always perfect. As my true memory serves, however, I think it best that persons who have not flown with babies of their own (by birth, adoption, or casual acquisition) should refrain from comment. God will indubitably get you someday for anything you unwittingly choose to say about controlling babies before you have experienced that quest.
Most babies have read very few travel guide books, don't understand the rules and, therefore, react out of pure instinct. When their little ears hurt, they scream. More power to them--it equalizes the pressure.
Try to reflect back on your behavior when you flew as a baby and judge these precious little human beings accordingly.
Actually, if the noise is that unbearable for you, it would probably be easier for you to get up and hike back to coach than to expect a mom or dad trying to cope with a miserable infant to take that trek.