Over the past few days, a senior member of the ANC and the leadership of SA's biggest public sector union, Nehawu, have exchanged insults. While the language has been direct and personal, this dispute might well be about what is probably the defining tension within the liberation movement: whether members of the Tripartite Alliance accept the ANC's decision to work with the DA in the national government.

The latest exchange of insults began at the weekend, when the ANC's KwaZulu-Natal secretary, Bheki Mtolo, said Nehawu members were to blame for the poor services many people received at government offices. He mentioned SA Social Security Agency offices, Home Affairs and the Labour Department.

In reply, Nehawu's KZN secretary, Ayanda Zulu, issued a statement referring to Mtolo as a "madman" and claiming (incorrectly, it appears) that he has a history of mental illness. He gave Mtolo 48 hours to retract his comments.

To be clear, this is a union, representing thousands of nurses, that decided its best possible response to a political statement was to use an insult based on mental illness. In the same breath, it claimed, incorrectly, that it was a "progressive" union. (The term "progressive" is going through a rough time.)

In Nehawu's defence, Zulu also said people received poor government services because of budget cuts and the policy of austerity.

Mtolo responded by telling Nehawu to "jump off a cliff" and refusing to apologise.

He told SAfm that Nehawu claimed the ANC's decision to work with the DA showed it did not care for "poor black people". He said, however, that it was Nehawu...