People who treat other people as less than human must not be surprised when the bread they have cast on the waters comes floating back to them, poisoned.
A fly may sting a stately horse and make him wince; but one is but an insect, and the other is a horse still.
The only cure for contempt is counter-contempt.
It's not a slam at you when people are rude -- it's a slam at the people they've met before.