Why did God get mad when they ate the quail?


Now a wind went out from the Lord and drove quail in from the sea. It scattered them up to two cubits deep all around the camp, as far as a day’s walk in any direction.  All that day and night and all the next day the people went out and gathered quail. No one gathered less than ten homers. Then they spread them out all around the camp. But while the meat was still between their teeth and before it could be consumed, the anger of the Lord burned against the people, and he struck them with a severe plague.  Numbers 11:31-33
            The people grumbled for meat and God gave it to them.  Then he punished them with a plague while they ate it.  Why?  Did God just snap or suddenly regret his decision?
            No, God doesn’t lose his cool or make mistakes.  His response, it appears, had something to do with the way they received the meat.  Maybe they didn’t pray or show thanks, just shoved the food in.  Maybe their hearts were ungrateful.  Remember, this whole thing started because they grumbled and complained for meat.  Wouldn’t eating all the quail you could eat solve their complaints or were their hearts still upset? 
            It seems the answer to their grumbling didn’t solve their grumbling.  God needed to humble them after blessing them.