I don't mean to be offensive but can't we tell the difference between how a word is used?

[Hestia]

4. Another victim of the dumbed-down education system - the word gay has several meanings

and 'merry' and 'fun' are two. It has nothing to do with the evolution of a word but the context of sentence.

There are such things as dictionaries:

3.
having or showing a merry, lively mood: gay spirits; gay music. Synonyms: cheerful, gleeful, happy, glad, cheery, lighthearted, joyous, joyful, jovial; sunny, lively, vivacious, sparkling; chipper, playful, jaunty, sprightly, blithe. Antonyms: serious, grave, solemn, joyless; staid, sedate; unhappy, morose, grim; sad, depressed, melancholy.
4.
bright or showy: gay colors; gay ornaments. Synonyms: colorful, brilliant, vivid, intense, lustrous; glittering, theatrical, flamboyant. Antonyms: dull, drab, somber, lackluster; conservative.

Hallmark has sold these (tacky) sweaters for several years.

Just shows that both sides have their pout-rages.