The argument is that leaders ought to have an understanding of which way they're blowing the wind - their own personal thresholds have little bearing on how far

The argument is that leaders ought to have an understanding of which way they're blowing the wind - their own personal thresholds have little bearing on how far the people they're speaking to will go unless the take a hard stance on where that threshold is. In this case, Trump at the very least failed to articulate beforehand where the line was, and it was very clear the line not being clear was a big problem. A secondary problem seems to be selective recognition of this: people are easily able to see the potential second order effects of Trump's rhetoric and react to it, but the same levers are not being pulled as actively when other people take similar rhetorical risks that have plausible deniability as contributing to violence for the reasons I mention.