Rather than shut it down, Google should have simply changed the response to something on the order of
...legally actionable libel.
Do you people think before you post these comments? Wait, I forgot, this is Slashdot. I must be new here.
Absolutely the only thing Google can get away with legally is simply ignoring the trigger. Otherwise they'll be illegally abusing their market position.
So is it libel or is it abusing market position? A reasonable belief that a statement is true is usually good enough to shut down a libel case, and that seems likely here. Google is not in the fast food business, so it's dominant position in the computer/web-ad market is irrelevant. You can only abuse your market position in the market you operate in. Did you even think before you posted your comment?