"A typical example of this is the word "gay", the latest polite euphemism for male homosexual, the latest of a great many."

Hmm... I'd have guessed it was less about being a euphemism and more about English-speakers wanting to have a one-syllable word instead of a five-syllable one, much like "straight" is a one-syllable word for "heterosexual", without this meaning that hetero sex is "unmentionably disgusting".

Not all pains have equal status as cause for complaint.

Even from childhood we know that pain caused by deliberate insults often hurts more than physical fights. People should not seek to take offense where none was meant -- but when offense is meant, and you know it's meant, not being hurt is often harder than ignoring a merely stepped-upon toe. A deliberate insult can linger all day in your mind when a toe is soon forgotten.