[Clinton spokesman] Josh Schwerin pushed back.
“This has and will remain a campaign about issues for Hillary Clinton, and that’s what she’ll continue to talk about on the trail,” he said in an email. “It’s disappointing Sen. Sanders and his campaign strategists have chosen to change direction and engage in the type of personal attacks that they previously said he wouldn’t do.”
The plausible explanation for this is that, for the left, bogeyman terms like sexist and racist have lost their meaning – they’re applied to all opponents, especially when they aren’t true, to numb and dumb the debate. They know there’s nothing real behind the words, and they’re surprised when their targets think that there is.