People who work at Harley say they were not the ones that cancelled this. It was Trump's idea. Spicer made a statement in his press conference today.
"Q Okay. And then the second question was, you mentioned tomorrow the meeting with the Harley Davidson executives. There's reporting that he was supposed to go to Milwaukee tomorrow or he was supposed to. That was canceled because of the company. Can you talk about that?
MR. SPICER: I just think -- look, it was easier for the executives to come here, considering the week and all of the activity that's been going on. And we figured the easiest thing to do was -- again, no decision had been made about or announced as to what we were doing. We looked at different options and, ultimately, the easiest thing to do in accordance with the President's schedule was to invite them here to Washington to talk about some of the stuff that we've been doing."
Although Spicer said it wasn't because of the protests my guess is that there was either a security concern and/or Trump didn't want the optics of protestors. He has a thin skin. Perhaps security didn't think they could provide adequate protection for the President with the protest threats.
If HD had cancelled it Trump would have been on Twitter already bad mouthing them and bringing their stock down.