Redefining a word to only be offensive is silly. Some words are bad, full stop. Other words have definitions that pre-date their offensive usage and are still used in regular speech.

Pointing this out to someone looking to be offended is an attempt to fight back at that nonsense. The original comment asking to use a different word was unnecessary and not relevant to the discussion in any way.

“Retard” is often used as a pejorative. I’ve never heard “retardation” used as a pejorative, when people use that word they seem to be using it correctly in a non offensive context.