From the Meditations of Marcus Aurelius, a book which I think you would enjoy reading:
From Alexander the grammarian, [I learned] to refrain from fault-finding, and not in a reproachful way to chide those who uttered any barbarous or solecistic or strange-sounding expression; but dexterously to introduce the very expression which ought to have been used, and in the way of answer or giving confirmation, or joining in an inquiry about the thing itself, not about the word, or by some other fit suggestion.
Be compassionate on ignorants and fools. That doesn't mean you should necessarily sacrifice yourself to try to put them on the right path. Just gently show them the right way, hope they will take the opportunity and move on.