Talking Back to the Village Idiot?

I occasionally write letters to the editor. Often my letters are in response to someone else's letter. Someone writes in and misrepresents some data, skews the truth on some issue or topic I hold dear. I feel compelled to correct their misinformation, to point out the inaccuracy. The problem I often encounter is that if I don't respond, those who read that first letter believe it. But if I do respond, some people think I'm as dense as the first person.

So the question becomes, how do you know when you're just talking back to the village idiot? (And is that really something you want to do?)

It's not always easy to decide...