I disapprove of Trump not because I think that he is a vile, mean person; we've had plenty of "mean" people in the White House who have been extremely effective presidents (Johnson is the best example; "the Johnson method" might as well be called "bullying"), and plenty of nice ones (Carter, Ford) who haven't been.
And I don't disapprove because his policy stances seem based entirely on impulse; by any measure his economic plans are predicted to be a disaster for both the US and the world economy, his protectionist stance towards our allies threatens our relatively secure status as dominant world power, and, of course, his policy positions seem to change from day to day.
However, I do disapprove of the fact that he is, plain and simply, a liar. It always seemed ironic that that title was usually attributed to Clinton, while Trump was considered as "telling it like it is," while even a cursory glance at Politifact (or really any fact checking website), will tell you that the opposite is true. And this isn't the type of white lying that politicians often require. This is the creation of an artificial reality entirely unassociated with our own, one where the US is running rampant with crime (it isn't), where our economy is in shambles (it isn't), and where immigrants and PC culture have stolen America from the Americans (it hasn't).
But there are people, particularly in rural ex-manufacturing areas, who are buying this reality because it gives them sorely needed hope. These people have legitimate complaints; the US economy is doing well...but not in their sectors or their towns, where jobs they've worked for generations are traveling overseas. They have a robust and valuable culture...that they correctly feel is becoming diluted by the (on-balance beneficial) influx of new cultures and ideas into the US. Donald Trump said "I alone can fix it," and they believed him because they needed something to believe in.
But Trump is a false prophet. His policies will hit the communities that believed in him the hardest, but Trump's deft denial of the truth may leave them in the dark as to who, exactly, pulled the rug out from under them.
I want to be wrong. I want Trump to uplift us all, but looking at how his proposals are slated to affect the US economy and foreign relations, looking at the baffling lack of experience in his cabinet, I don't think he has the knowledge, nor possibly the will, to do it. He has exploited the desperate to gain power, and that exploitation is what I disaprove of the most.