Be careful of definitions !
There are citizens who are unhappy, shown by the red faces in the happiness display (you get one of these per population point, for example, complaining that "it's too crowded"), and there can be angry citizens, who show up in red below the specialists display when the city has more "unhappy" citizens than "happy" ones. Unhappy citizens still work: angry ones don't, and these are the ones to avoid. They still eat, but produce nothing.