They get this stuff from their life experience and environment. Most contemporary politicians are over 50. Which means that they were raised with parenting practices based on cruelty, manipulation and violence. This is how the world works for them.
As for conservatives, they usually come from conservative / religious background, which instills beliefs like "being rich is the result of being disciplined and being moral, ergo poor people are lazy and immoral," and "if violence doesn't work it's because you're not using enough of it", etc.
For more on this divide see George Lakoff's "Moral Politics" lecture. Completely changed my outlook on political (or any kind of PR) messaging: https://www.youtube.com/watch?v=5f9R9MtkpqM
Also, to him (and many representatives of his community), what he is doing is moral. It is a righteous battle that someone with enough guts needs to fight.
So, he is a "good guy"... raised in a certain way and programmed with certain beliefs which cause him to see good in a way very different from me (and possibly you).