I think the distinction is between opposing a pol's agenda, which is appropriate, and labeling his supporters as worthy targets of nutcase violence, which is clearly not, at least it wasn't until recently.
I'm talking about saying things like "he's not my President" or not accepting he is the President or calling him out as a occupier and other rhetoric - which many, many conservatives did the entire 8 years Obama was in office. And now they cannot understand why people on the left say Trump isn't their President or he's not the rightful President, etc. Same shit, different side.