Former Cosatu general secretary Zwelinzima Vavi and EFF leader Julius Malema are plotting to overthr.
South Africans had shown little respect towards blacks and their culture, The Star reported him as saying.
Nzimande backed the call made by the SA Communist Party in KwaZulu-Natal on Monday, for a law protecting the presidency from attacks that were “unfair, and lacking in fact and truth”.
He warned that Zuma supporters would soon reach boiling point.
“People can differ with me and you can insult me as you like, but disrespect, that is not acceptable,” Nzimande, the higher education and training minister, was quoted as saying by the paper. “We are being undermined by whites.”