The Washington Post had a front page article on this incident this morning. They don't make much if any distinction between "news" and opinion pieces any more, so it was hard to tell which it was supposed to be, but they just blatantly lied about what the video showed. I have watched all the videos and all I saw was the guy brushing past the reporter as she tried to approach Trump, perhaps he grabbed her arm, tough to tell and she turns her head. No violent grabbing or pulling, as implied in the Post article.
The media/left like to create a false narrative and treat it as factual, eg republican war on women, Trump is a liar ( but not Hillary), etc. They see this as a golden opportunity to turn the tables on Trump and for once, set the agenda. Now it is Trump hates women and defends an assault on a woman.
They are totally ok with Bill Clinton violently assaulting women and Hillary directing intimidation efforts at those women. A reporter has her arm briefly tugged at and it shows Trump is a POS.