First, could we please call a moratorium on the word "evil"? Fictional characters like demons and arch villains in comic books are evil. Humans don't have supernatural powers. Instead, we are depraved, craven, and insane.
As Arthur C. Brooks wrote in his Valentine's Day piece "Raking Risks in Love" in the NY Times, the opposite of love is not hate.
I agree. Hate is not the absence of love. What makes hate singularly bad is the violent ideation it comes with. The ideation does not always evolve, but it can. If it does not, it simply harms the hater and those around him or her. Hate is pain that takes up residence in a person's schema and slips behind the wheel. There are ways to deal with this intruder, but they require courage and grace. It is easier to morph from a person into a hater than it is to seek help or grant forgiveness.
Hate leads to undermining, sabotage, gossip, rumor-mongering, defamation, bullying, verbal and physical assault, and murder. Expressions of hatred can be done remotely or in person. Triggers for hatred can be other people's behaviors, genotypes, genders, or their coincidental embodiment of memories/feelings/acts in the hater's actual past or imagination.
Haters use their words to wreak havoc on their targets' psyches, reputations, and relationships. Haters maim their victims, taking them out of the game of life in slashing and acid-throwing tantrums. Haters are angry cowards - many poison or bomb and run. Kamikaze haters are not brave, they are brazen and fanatical and lack autonomy, replacing pride in themselves with pride of their nation, their religion, or their point of view, be it their own or some other zealous idealogue's. Haters are selfish, letting their desperate need for resolution, payback, and control grow beyond reason. Their pain and fear are immense.
Not everyone who does harm is a hater. But many haters do harm. This is what makes hate a word our parents do not allow us to say out loud when we're kids. Unlike evil, hate is real. Toxic. Contagious. And growing.