It isn't necessarily evil to tolerate and evil person in the sense of being kind, but you make a vary good point about what it is they demand we tolerate.

What you said about their words is also a good point that should be brought up often. It was an effective tactic to mess with the language, but even though things have gotten to where they are, we should never let them vomit up the word salad without challenging them. The trick is to do that firmly without descending to their level of vitriol. As for being kind, repaying evil with good never means we don't tell them the truth when it might hurt their feelings, which is how they stopped the mouths of the timid (also a tactic). Jesus never spared the feelings of the Pharisees or even His own disciples when He was telling them the truth.

They get feisty because they want to provoke a reaction so they can deflect their own guilt have the baseless justification to say, "See? See? You're just a hateful bigot!" But they have no way to handle a person who can speak the truth firmly without an emotional display, and their own accusations will accuse them. You might hope to convince them in a moment of revelation, but that isn't the primary issue in a confrontation. The primary issue is telling them the truth. Jesus had hope that his disciples would heed it because they were goodhearted to begin with, but He had no such expectations for the Pharisees who wanted to kill Him. He told the truth to them anyway, and it sealed their fate when they wouldn't listen.

Even so, we should tailor our message to the audience. It helps to have the discernment to know who are the true swine and who might be ready to leave the pig trough.