"Words, of course, are the most powerful drug used by mankind." - Rudyard Kipling
All politics is based on a friend/enemy distinction. That dichotomy is narcissistic - "I am right and good, and you are wrong and evil. So if we get rid of you things will be great."
Propaganda is based on our narcissism. It is, however, possible to use propaganda for good purposes. Rarely.
It's best to know how propaganda works (that it is based on our narcissism, our ability to split things into all-good and all-bad), to immunize yourself against it.
Edward L. Bernays, who was Sigmund Freud's nephew, was nicknamed the Father of Spin, since he was the creator of modern propaganda techniques. Which he used to muster public support for President Woodrow Wilson's war - World War I. The one that ushered in the destruction of the 20th century.
Bernays found propaganda had three characteristics:
Stress emotion over logic (but make people think they are logical).
Demonize the enemy (make them think the enemy is evil).
Promise a "war" that will make the world safe for goodness (a better world, one without evil).
Notice that propaganda bypasses reason. More accurately, reason is in about third place.
Scott Adams, he of "Dilbert" fame, claims that in first place is identity, that is, getting people to emotionally identify with you. That means they have to identify with you as the good guy who will do good things for you.
Second is metaphor, then third is reason.
When Trump called Bush "low energy" he was saying, "He is [metaphorically] a sloth." He was ridiculing him. (Voltaire once wrote, "Lord, please make my enemies ridiculous.")
Propaganda can be used for good or bad. Hitler, for an example, was a master of propaganda (the section on propaganda in Mein Kampf is essential reading).
Hitler claimed groups are feminine, that is, ruled by their feelings - which means they aren't using their reason. Groups never do.
Trump is a natural master of propaganda, although I'm sure he has studied it to get the techniques right. He is getting people to emotionally identify with him (emotion over logic).
He is mocking his opponents as fools. Not exactly evil, but incompetents, buffoons. Bad in all ways for the country.
He's claiming America will be a better place with him as President - not that evil will cease to exist, but America will be "great again." With a minimum of "evil."
Since people are emotionally identifying with him (seeing him as the good guy), they are automatically seeing the people he attacks as anti-American. The "bad guys." This helps him because most of them are - and when they attack Trump they are cutting their own throats. Hillary found that out the hard way.
Trump is refusing to let people define him as a liberal or conservative. This is a good thing. Don't let people define you.
He is in fact a populist and a nationalist. He's getting people to define these things as good things - which means "conservatism" is in complete disarray - which is a very good thing. Now leftism needs to be destroyed.
When you let people define you when they are your enemies they will always try to define you as evil. Then the rest of those propaganda techniques kick in - emotion over logic, demonization, attempts at destruction.
It's what Trump's opponents are trying to do to him - define him, see him as dangerous, try to destroy him. Guess what - it's not working.
If you put all these techniques together this is what you get: get people to emotionally identify with you as the good guy. They will automatically see your opponents as the bad guys.
Attack your opponents through ridicule (one of the main techiques used by the anti-American commie Saul Alinsky in Rules for Radicals (this is where metaphor comes in). People will see them as oppressors only out for themselves - which means against you.
Your opponents will end up demonizing and destroying themselves.
Identifying through emotion, demonization and ridicule of enemies, then destruction of them to create a better world. It's that simple.