Trump is a way out of the shell game that is politics today. Trump makes people and the elites uncomfortable because, well, he says stuff that people actually are thinking. Why does the US have to educate and support generations of illegal immigrants from Central and South America? Where is the responsibility of the Latin governments? Why does the US consider Saudi Arabia an ally, when half of the time they're working against US interests? Who really does benefit from free trade?
Why does the US have to educate people who live within our borders? We would be much worse off if we did not. And, having those people within our borders and taking jobs that full-blooded citizens would not take allows industries to exist in the US which otherwise could not.
Where is the responsibility of Latin governments? Within their own borders. They don't enjoy their workers leaving either. It is silly to believe that they are somehow benefiting from this situation.
Why does the US consider Saudi Arabia an ally? Well, the Cliff's Notes version is that we can have no allies in an area of the globe, or we can have imperfect allies. Insisting on sycophant states around the world is never going to work.
Who really does benefit from free trade? Generally speaking, the world benefits from free trade. On a selfish level, the US benefits less from free trade than more impoverished nations; the debate is if it is better for us in the US for the world economic level to rise year over year and for the average US citizen to be less extravagantly rich compared to the world average, or if we should prefer the world economic level to stagnate or even fall if it means that the difference between the average US citizen and the average world citizen gets wider.
Back on topic, the problem with Trump is none of this. The problem with Trump is that he is a demagogue. He incites fervor by giving easy answers to problems. Immigration? Build a wall (for $10B while the most generous estimate for what he has described is closer to $500B-$1Trillion just for the Mexico border, and that wall can be tunneled under and climbed over or swum around). Terrorism? Ban Muslims from entering the country (violating the Constitution and all precedent, and setting a nice big fire under the "holy war" rhetoric used by Jihadist factions to do harm to the US). "Obamacare"? Throw it out and let insurance be sold across state line (ignoring every economist who predicts a rapid race-to-the-bottom to the most permissive states and a skyrocketing of insurance and office administrative costs). Gay marriage? Trump opposes it (a hit for the crowd he is currently courting, as though he could do anything as President to put that genie back in the bottle). Foreign countries say bad stuff about us on Twitter? "Shut down the internet" in those countries (ignoring that that is practically impossible and the only effect it would have is to make the US look like more of an ******* than we already look like). ISIS gaining control of some Iraqi oil fields? "Bomb the hell out of" them. Oh, and kill their families too. Torture is banned by Geneva conventions? Pass a law to make them legal again, because the "bad guys" do worst and we're in the third grade where an excuse like that actually apparently sounds reasonable to some people. And we haven't even hit on his comments about how to deal with world leaders.
Demagoguery works to get people elected. It always has, since the first recorded examples in ancient Greece (where, in fact, the term comes from). It is a flaw in the system of democracy (especially representational democracy, the variant we follow here in the US) just as intrinsic as monopolies are a flaw in capitalism. As with monopolies, when the "system" fails, rational people need to recognize that and enhance the "system" so that it can not fail again or can at least defend itself from someone exploiting the weakness for their own personal gain. What demagoguery has never, ever accomplished is increasing the prosperity of the country upon which it is inflicted. The closest it has come is when that country - 1930s Germany as a prime example - is so beaten down that there is only upward potential, but even there most historians agree that the demagogues in question hurt their countries far more than they ever helped it.