It's quite a slap in the face considering all the people across the country who were willing to risk being assaulted by leftist goons at Trump's rallies. They went anyway. They waited in lines for entire days. And this is the thanks they get.
A line has been crossed with this betrayal, IMO. And not just for Trump, but for the entire American political system. This was, to many people, their last go at a good faith political effort. The DC establishment has erred badly with this.