How do the court messengers react to being called Ashy buttock?

The kotma,or court-messengers, are low-level functionaries of the colonial regime. Their job is to bring men to the District Commissioner for trial; they also guard the prisons. Due to the gray shorts they wear, they've earned themselves the unflattering nickname of "Ashy Buttocks." The Igbo people despise them, not just as foreigners, but as the white man's lackeys, and this insulting expression perfectly encapsulates their utter contempt and loathing.
As one can imagine, the court-messengers are not exactly thrilled to be the object of such name-calling. They take themselves and their role very seriously and so don't take kindly to being subjected to verbal abuse.
Prisoners in the jail have written a little song which they sing when they're out cutting grass:

Kotma of the ashy-buttocks. He is fit to be a slave. The white man has no sense. He is fit to be a slave.

The court-messengers are very angry whenever they hear this song, and furiously beat any man they catch singing it. But they cannot stop the spread of the song in Umuofia, where it becomes very popular as an expression of the Igbo people's growing opposition to colonial rule.