On Thursday, the dollar gained strength when ECB President Mario Draghi introduced a new action plan. European stocks soared, and it triggered a wave of selling in the S&P 500 futures.
"But that buying was a stupid as you can get, because the dollar was flying higher at the same time that the European stocks roared up, and the strong dollar is bad for us," Cramer said.
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As soon as stocks jumped, Draghi hinted that, with interest rates so negative, the ECB might not take further action. European stocks plunged, and so did those in the U.S.
Some of that drop was caused by oil, but Cramer attributed the rest to investors trading with Europe.
"If these traders were my students in the classroom, I would give them all Fs and make them sit in the corner with dunce caps on," Cramer said.
The "Mad Money" host says the stupidity increased when Europeans assumed Draghi was also done with his multiyear attempt to weaken the euro to give European companies a competitive advantage to the rest of the world. This fear caused the dollar to weaken versus the euro. At the same time U.S. stocks were crushed, and U.S.-based international companies led the way down.
Cramer thinks this is lunacy.
U.S. based international companies should have gone up, not down. From this ridiculous action, he drafted the following lessons:
No. 1 Never chase stocks. It is not worth it. It is better to say you missed it and wait for the next downturn.
No. 2 When the market rallies, try to figure out why. Even if there is a real reason, it's worth waiting for lower prices before pulling the trigger.
No. 3 Wait for a market-wide pullback before buying. The intra-day decline was a classic buying opportunity for Cramer.
"It has been a winning strategy longer-term, even if there is no instant gratification," Cramer said.