Why not? From reading the article under the link, the impression is that this professor had a habit of telling politically incorrect sarcastic jokes in audiences that (for whatever reason) tended to be sympathetic to his views. He got an e-mail from that Society of Black Engineers and replied in a similarly sarcastic fashion, without realizing that those Black Engineers are not his usual audience. He did not know what the academic world was like outside of his usual circle of interaction, that's what his naivete consists in.