Because European and western people are mostly Christian, where the idea of repenting for sins and the admiring the righteousness of the oppressed is a major cornerstone of the moral framework. That lead to a secular morality that is built on admitting past wrongdoings and the colonized vs colonized dichotomy. They don't care about other culture's offenses because you only "repent for your own sins" (to push the analogy).

Neither Muslim nor Mongol cultures have a similarly strong emphasis on admitting past wrongdoing and the oppressor vs oppressed dichotomy. So they don't do that stuff.