Tender is the Night: Fitzgerald

Man is venerable only in his pride, but delicate as Humpty Dumpty once that is meddled with.

Good manners are an admission that everybody is so tender that they have to be handled with gloves.  Now, human respect - you don't call a man a coward or a liar lightly, but if you spend your life sparing people's feelings and feeding their vanity, you get so you can't distinguish what should be respected in them.