I think Mr. Clarke is too sensitive.
"The Boston Free Speech Coalition, which organized the event, said it has nothing to do with white nationalism or racism" -- from the article. There were other similar sentences in the article.
There was also a sentence that the Boston group formed as a response to college campus speech codes.
I couldn't find any info online on the Boston group. 
This is an instance, Mr. Clarke, where you made connections or saw slurs that didn't exist. The article didn't make the connection you saw. 
I don't know enough about the events in Boston, but if conservative groups in Boston did come together to promote free speech, and some liberal groups got their nose bent out of joint over it and caused the organizers to cancel the rally, whose fault is that? Not the groups who organized the rally.
If people hold a free speech rally, white nationalist groups try to horn in on it, and other groups interfere, whose fault is that? Not the people who organized the rally.