just admit you screwed up, dammit.
I have nothing in particular against people who occasionally cut and paste an item or article from somewhere else and present it as a blog entry. I don't even mind it TOO much when they don't bother to look into the origin of the item and post it with uncritical approval or endorsement.
What I find completely objectionable is when someone points out something clearly wrong with the item in question (which may range from a mere incorrect attribution up through line-by-line debunking of every single point presented), and the original blogger says "Well, I don't care, I only posted it for amusement value" or some such similar lame excuse, closely followed by "No, I'm NOT going to change the original article; why the hell should I?"
Well, I'll tell you why: because the information that you posted was WRONG in some way. No, you didn't originate the error, but you disseminated it. As such, you have a modicum of responsibility to also disseminate corrections when new information becomes available. Unless you want to become known as an unreliable source, you owe it to your readers and yourself to admit that you got something wrong, and make it right. Stonewalling about this will only make you look stubborn, closed-minded, and mean-spirited.
And while you may BE stubborn, closed-minded, and mean-spirited, you probably don't want people to think that about you.