Rhetorical criticism is fairly common and vital, as the message and the medium are pretty closely intertwined. The twists of words Stallman uses are to cause a guttural reaction to what he is saying and to try to evoke a populist response. Much like speeches by recent political figures, such as Donald Trump, Stallman's rhetorical style will agitate people who already support him, but alienate him to the greater number of people who disagree with him.
As much as people try to claim that the medium doesn't matter, it does, a lot. Stallman is a poor user of the mediums he is given, and as such, the points made are difficult to discuss. Were he to use less slanted language, and stick to the facts, he would be more effective in getting his point across, and would not open himself, or his arguments, to such criticism.