From categorization to categorism
To properly understand these four concepts, we need to relate them to the benign concepts of which they are dark shadows. These are categorization, preconceptions, preferences and choices. Four benign and generally unproblematic concepts.
Every human culture and individual human being uses categorization. Human brains and social structures are wired that way. But while it would be neither possible nor preferable to stop categorizing altogether, we need to be careful with what categorizations we make and how we use them.
Every human being uses preconceptions, and every human culture takes certain preconceptions for granted. The simple fact that we never know everything would bring us to despair and apathy if we didn't fill the gaps with preconceptions.
Every human being has preferences and other feelings. Every cultures encourages and cultivates some preferences and other feelings. Without this, we might never belong anywhere. Or ever feel anything but an empty void.
Every human being and group of human being makes choices in one way or another. Freedom of choice is important and precious. But freedom for who? At what terms?
Somewhere along the way on a sliding scale, choices turn into discrimination. Preferences sours into bigotry. Preconceptions stales into prejudices. The whole thing thus becomes a matter of categorism rather than merely a matter of categorization. It has ceased to be a tool for understanding, instead turned into a mental prison, a social prison or a dirty weapon. Note that the shift is a subtle gradual process. Often a matter of how free from categorism or how tainted by categorism something is, rather than being a matter of being categorism or not categorism in absolute terms.
For example, it is a rather reasonable categorization to claim that some people can be considered "men" while others can be considered "women". It stops being reasonable as the claim expands to insinuating that women are inferior to men, that women are dirty, that men are evil or that everyone who is of a certain gender think and feel in a certain way.