I'm not a breeder and mostly just tease people who are because it's fun. Seeing people respond with outrage that we don't think they are special because they managed to pull of something that 99% of the population can do is kind of fun.
But I do have a theory. If, from an early age, traveling simply becomes "part of life" you have a much lower chance of having a meltdown than if your kid never leaves the house.
I've got friends and family who just stay at home with their kids. When they do finally decide to go to the grocery store it is a HUGE event and the kids freak out. I've got friends and family who have continued to live their life despite having kids and while there is the occasional meltdown, the kids are usually awesome. They're also a lot more inquisitive about the world.
As a brat that was dragged around the world for most of my life, I understand families have to travel. While baby proof planes would be amazing, expecting that is pretty unrealistic. Kids freak out for no reason, that's just part of life. I do feel bad for the parents when it happens, and despite my desire to gate check the child or stick them in the overhead bin, I try to offer a glimpse of understanding. But I completely believe that having kids is a choice and it is pretty damn disrespectful to bring one who is likely to have a meltdown into situations where it is likely to disrupt the atmosphere for people who can reasonably expect a certain, peaceful environment. Movies, spas, first class on an airplane are some situations that come to mind.
Additionally, an airline needs to have a clearly defined policy for situations like this. Both the passenger and the employees need to know what to expect.