What rankles Kenophobes the most is that he does in fact speak his mind in perfect plain English, rather than the incredible Twitspeak of Bonkers and the rest of the tory Junior Drones club. And totally unlike the featureless, sterile flat-pack jargon of the regulation emasculted prawn politicians in Westminster or your Town Hall. Look at any of his speeches or interviews.
The sneerers simply don't like what they hear, and prefer round vowels and the comfort of being patronised by the upper classes, no-matter what debased form they manifest themselves in. The idea that someone as common as Ken could actually be more capable and articulate than a toff drives them crazy. But you have to remember that they are at the end of the political spectrum which just loves obedience, to the point of masochism.