A lot of Americans think it would be better to have a businessman than a politician as president, and I sympathize with them. Alas, the only businessmen crazy enough to run for president seem to be, well, crazy. At least Ross Perot kept his craziness confined mostly to private matters, such as the looming disruption of his daughter's wedding. Donald Trump puts it front and center.
From a libertarian point of view — and I think serious conservatives and liberals would share this view—Trump's greatest offenses against American tradition and our founding principles are his nativism and his promise of one-man rule.
Not since George Wallace has there been a presidential candidate who made racial and religious scapegoating so central to his campaign. Trump launched his campaign talking about Mexican rapists and has gone on to rant about mass deportation, bans on Muslim immigration, shutting down mosques, and building a wall around America. America is an exceptional nation in large part because we've aspired to rise above such prejudices and guarantee life, liberty, and the pursuit of happiness to everyone.
Equally troubling is his idea of the presidency—his promise that he's the guy, the man on a white horse, who can ride into Washington, fire the stupid people, hire the best people, and fix everything. He doesn't talk about policy or working with Congress. He's effectively vowing to be an American Mussolini, concentrating power in the Trump White House and governing by fiat. It's a vision to make the last 16 years of executive abuse of power seem modest.
Without even getting into his past support for a massive wealth tax and single-payer health care, his know-nothing protectionism, or his passionate defense of eminent domain, I think we can say that this is a Republican campaign that would have appalled Buckley, Goldwater, and Reagan.