Fool me once, shame on you. Fool me twice, shame on me. The old saying is a simple reminder that once burned we should learn not to touch a hot stove a second time. Or, put another way, once someone dupes us we should not swallow the same bait again.

Yet, that’s exactly what has occurred Monday. After the rating agency Standard and Poor’s decided to lower the credit rating of the United States government late Friday, stocks spiraled down on Monday.

When the dust settled, the Dow Jones average was down 5.5 percent, falling more than 630 points; the S&P 500 index fell 6.7 percent.

While a number of potential sparks set off the skittishness that led to Monday’s cliff dive, clearly S&P’s assertion that the U.S. government’s ability or willingness to pay its debt was in question was the largest motivator that started the snowball rolling.

The government can clearly print as much money as it wants — though doing so without restraint causes a whole boatload of other problems.

However, the ludicrous thing is the level of respect the markets are giving S&P in the first place.

How quickly we all forget the housing mess that cut the legs out from under the retirement savings of millions of Americans in 2008 and 2009.

The biggest piece of financial dynamite at the heart of that explosion was the mortgage-backed securities that S&P clearly labeled as “safe to handle.”

We all know how many fingers and toes were blown off in the years that followed.

We know the company screwed up a few years ago leading to the 2008-2009 financial meltdown, so why do we all care so much about what they think now?

Hopefully, calmer heads will prevail soon.