Think mob mentality. Think politics of personal destruction. Think about what the Left calls people they want to destroy, to make radioactive. Sexist. Mysogynist. Racist. Homophobic. Islamophobic. Xenophobic. White Male Privilege.
The Left hates Trump because the people who lead the Left hate Trump, as darkness hates the light.
Trump proves them wrong about literally everything, and they cannot tolerate it.