To divide ourselves and others is only human, otherwise we wouldn't have races, phrenology or political parties
An outside division is easier to see.
When we divide others into categories we're being "logical," when others place us in a category they're being racist/sexist/agist/intolerant. Forgetting the log in our own eyes it seems
We are so accustomed to dividing that we often divide ourselves- I'm a human bento box... it happens, we're all control freaks in a way and divisions are a manner of controlling.
To name is to have power, to divide is to get power over naming. Look at the scramble for Africa