“...most of the other candidates haven’t been jerks with Trump at all.”
Trump was referring to the Cruz’s lying ads that he is running in South Carolina. Just because they all walk onto the stage does not mean things are a clean slate.
It’s not just the rudeness by the candidates themselves, though I think Trump still wins there. It is the rudeness here, and how so many Trump supporters are flat out nasty to anyone who doesn’t support their guy. It is counter-productive as hell, and I’m amazed more of you can’t see that.