> If it is a universal truth, then there shouldn’t be any exceptions to the rule.

Have you give that much thought?

> But if everyone understands the word ‘horse’ to mean a certain animal, why waste so much of an argument asserting that ‘true’ horses are actually deer?

A horse is a concrete object; hardly a contentious matter. A better analogy would be the word ‘love’. Nothing wrong with pointing out that few people use the word in anything but a disastrously superficial sense — many of our admired thinkers have said as much.