Without concern for the proper use of words, language becomes useless.

A valid point, as long as you're careful that language work for you and not vice versa. The moment you find the expression of your concept being stifled by grammar or vocabulary or tradition, find another way. Invent a new word; define it using comparison, differentiation, pictures, hand signals, noises. Language should bend to incorporate reality; otherwise the tail is wagging the dog. Language has enormous power to make our world, hence the sort of typical argument Eliezer discusses. But we should never lose sight of the fact that it is our tool, and any rules should be enabling rather than restrictive - clarity of communication is the goal.