What or who is going to win a given struggle is only in a small way determined by how the forces look on paper.  Motivation, skill, training, leadership, domestic support, what the locals think, and all sorts of other things, including luck, enter into it.  It's the course of wisdom to avoid conflict even if one feels oneself significantly stronger.

Matters of courtesy and respect require common sense, but using examples where common sense makes the rule obviously inapplicable is "slippery slope" fallacy, and, to my mind just someone looking for excuses to engage in racist or sexist, or whatever, behavior.

So, for example, if someone were to whisper to you at a party about someone nearby, "You know, she's a dyke," (a mildly derogatory reference to a masculine lesbian), almost always one would let it pass except maybe change the subject or maybe excuse oneself and find other company.

I would say that being offended by such things, just as being offended when someone is disrespectful, does no good and the only harm is to oneself.  It's like when someone uses a harsh obscenity or commits a grammatical error or other faux pas -- our getting upset only raises our blood pressure, not theirs.

Still, it also seems to me that one cannot let especially bad bits of racism and other such things go unremarked.  This is tough.  It may be a cultural blindness (as what happened to me once when I used the word "spastic" in central England -- it seems this word is taboo in Britain but of course frequently heard in the States without offense.  The thing is, care is needed when protesting to such things, as one is more likely to reinforce the prejudice than anything else.

It may also be deliberate crudity for humor or a thrill or just a bad habit. I tend to avoid associating with such people, especially if they rationalize or complain about political correctness.  They aren't worth my time and I figure they say similar things about me when I'm not there.

We should only follow our mind and what we can see is sensible and fits the evidence, and even then never with  absolute belief or faith but only with well formed opinion.

Following what we find beautiful or makes us happy to contemplate or gives us joy or any of those things is the well-traveled road to regression and disappointment.  Peace and lasting happiness comes from accepting what is and not chasing rainbows and mirages and other things we would like to be the case.

There is such a thing as a sociopath -- a person commonly described as without a conscience -- and I suppose if you put that in the same person with a strong sexual sadism perversion, one would have a product we would easily call evil.

This however doesn't address the point I was making which is more philosophical and not psychiatric.  To call a person evil is a judgment and I think it is not only morally wrong but also unscientific and simply a  mistake to make judgment calls about people, good or bad.  The individual described in my first paragraph is extremely unlucky  to have such an inheritance or development, and needs help and deterrence, but thinking of them as evil distorts the reality.  They act out of internal desires and instincts, not much different from a cat playing with a mouse it has caught rather than dispatching it immediately.

In short I think evil is a word generally best avoided or just used as a form of shorthand to indicate strong personal disapproval but not as a description of something real in the world.