What a terrible comparison. The best comparison in this case would not be shit, but, say, a one hundred dollar bill. Someone might throw it on the ground, step on it, knead it and throw it in the shit, but it will still be a one hundred dollar bill, which is always worth one hundred dollars.
Well, about the crying baby, I already mentioned parents need patience, it does not have only an upside. About your sister, well, I don’t mean to offend or judge, but it is your parents fault to give her everything she wants. All good parents I know, including my own, just won’t tolerate such behavior and they will do anything to prevent the little kid to have everything it wants, doesn’t matter if they have to tolerate the screaming and crying.
An ant of mine told me that once she was in a supermarket with her son and he wanted something. She said no. Then her son started crying, calling everyone’s attention. She told him to stop, he did not. Then she said: “If you keep embarrassing me like this in the middle of the supermarket, I’ll leave you here.” Obviously, he kept crying, so she left him there and went away. Then my cousin stopped crying, ran after her and apologized, saying that he would never do that again.
The problem is most parents don’t have enough courage to do such a thing. Of course my ant wouldn’t leave my cousin there forever, it is a matter of using toughness to show in practice that the kid won’t have all that it wants by screaming and crying. But normally people will just want the kid to stop so they will do the simplest thing that there is to do, which is to make the brat’s wish. That is an obvious but unfortunately common mistake. Parents need lots of patience and also to be psychologically stronger than their own child, which is not always as simple as it sounds, since you have much more to do than your child, who will dedicate its time in learning how to get what it wants. But it is possible, since (supposedly) you are much more experienced then a kid.
It’s each one’s choice whether one is ready and willing to deal with children. It is not always so simple to deal with them, and sometimes, no matter what you do, things get out of your control. But kids aren’t inherently little devils you just don’t have control over, this is a very bad misconception like many others that the modern society have (and it has way too many). And many times kids will amuse you (the OP being a great example) and make you proud of them. That pays for the trouble you have raising them.