The ugly attack on Iain Duncan Smith by five protestors at the Tory conference in Manchester has been widely seen as another illustration of how dangerously embittered British politics has become. We now live, it is often said, in a world of deepening friction, hate and intolerance. Angela Rayner’s now notorious rant about Tory ‘scum’ was also seen as a prime example of the spread of ‘cancel culture’, or the way Twitter rage has ruined civilised debate.