A student* asked me a few weeks ago: "Miss, you're one of those people who's really nice, up until the point where you're just... Well, not... Aren't you?"
I hemmed and hawed for a bit before I looked at her and said, "Well, my basic philosophy on life is this: so long as we all play by the nice rules of polite society, everything is fine. The moment that someone breaks those rules in regards to me, I don't feel like I have to play by them either. I think that's fair."
She just looked at me and said, "I'm not sure if I now really like you, or if I should be scared."
...And yes, I do believe in karma.
*Not my student, just a student on campus.