Anti-mask laws are mostly the result of masked terrorists like the KKK who exploited anonymity to commit their crimes[1].

> Many anti-mask laws date back to the mid-20th century when states and municipalities, passed them to stop the violent activities of the Ku Klux Klan, whose members typically wore hoods of white linen to conceal their identities.

[1] https://en.wikipedia.org/wiki/Anti-mask_laws#United_States