Professor Kingwell is obviously not actually proposing curbs on free speech, nor is he saying that people cannot be reasoned with or eventually come to be reasonable, but he is saying that spending too much time attempting to reason with those who show no interest in being reasonable no matter how much energy is expended attempting to understand their perspective, is a fool's game. That seems a rational and real-world based position which has merit. 

In those circumstances, I can see the usefulness of a social structure built around intolerance for trite talking points and slogans, imprecise speech, PR and message control, style over substance, social media shaming and faux outrage , political polling and question manipulation,  echo chamber media cheer-leading, identity politics, and not to be forgotten, the oft used , virtue signalling