People don't have some kind of right to only hear sounds that they find pleasurable as they go about their day. If you don't want to be subject to crying babies, screaming kids, or whatever other sounds you find annoying, stay home. That or suck it up and deal with it.
That said, parents need to step their game up. If a toddler or young kid is throwing a screaming fit in a restaurant, store, park, plane, train, or automobile, it's probably because his parents are lames. It's not that hard to have kids that aren't out of control. Now, if an infant baby is crying, that's a little different and far more difficult to control, but one could certainly step outside with the baby until they could soothe it. Parents need to be more considerate of others when their baby is being disruptive, others need to grow up.