1) Cultures contain multitudes. The fact that there are negative idioms present in American culture doesn't mean that every American is always acting negatively; nor does it mean there are no positive idioms.
2) You are redefining the idioms to be much narrowly used than they are in practice. Additionally, the list of such idioms is nearly endless... people will say "might makes right" to argue that the more powerful entity can do whatever it wants and shouldn't be restrained... they'll say "history is written by the victors" both as a reminder of the flaws in history, but also as a call to ensure that their team is victorious regardless of what it takes.
3) I'm capable of googling. But the fact that a bunch of weird youtube videos claim something is an idiom does not, in fact, make it an idiom. The phrase exists, but I couldn't find it in a print corpus at all, and when I found it on the web it seemed to be used by people ranting about dishonesty, example translation: "people who steal money, steal food, cheat in school, robbing society, cheating whenever they can, don't they have any shame at all??" or "Taiwan is in a moral depression; some people are not ashamed and will not hesitate to cheat if they can".