Allegedly, British strikers in the 40's, maybe earlier. The phrase itself is older. https://en.m.wikipedia.org/wiki/ACAB
Might have been used by any number of groups upset with police. It's anti police.
Why are you trying to associate it with racist skinheads?
Why are you trying to associate it with racist skinheads?
It's a 1 month old account. Not a hard guess.