What if it isn't everyone who uses a word "wrong"? What if it's say 25% of people who use it incorrectly? Should you encourage them to use it correctly?
If there are two different ways of using the word and they could be mistaken for each-other that's bad. Once the use of a word has flipped and means something very different from the original (idiot, gay, etc.) then there's no reason to try to return to the original usage. If the usage is still in dispute and the majority of people use the word in the original meaning, I think it's good to discourage people from using the word incorrectly so that people are still able to understand each-other.