Here's a common issue that comes up with letters to the editor, and my response:
Dear Mr. Furst,
A few weeks ago there was a letter to the editor with a totally unfounded explanation for climate change. Although you later printed a letter by Marge Hake challenging it, that does not undo the harm of publishing the original. You should be doing everything possible to get the best scientific facts about what scientists like James Hansen (who has been tracking it for 30 years) say is in store for the planet as the century unfolds. As you know, these same scientists are shocked to find that their predictions continuing to become more dire by the day.
Thanks for this, Darlene -- we can't really get into fact-checking letters to the editor (except for flat-out errors like a name misspelled, etc.)...letters are understood to be opinions, many of them matching up with facts and many not...personally, I think the same can be said of syndicated columnists...the best corrective is always letters from other perspectives.
I'll look at that letter again, though...if there was something ridiculously false on the face of it, we should have sent it back to the writer for addressing.