A, when the body temperature is lower than normal, the discharge frequency of cold-sensitive neurons is higher than that of heat-sensitive neurons, and A is correct;

B, because the hypothalamus is the center of body temperature regulation, when the human body is in a hot environment, the discharge frequency of cold-sensitive neurons increases, while the discharge frequency of heat-sensitive neurons decreases. Through neurohumoral regulation, the body's heat dissipation increases and heat production decreases, and the body temperature returns to normal, B is correct;

C, if the human body temperature continues to be high after being infected with influenza virus, and the body temperature is higher than the normal value, then point S moves to the right, and C is correct;

D, the normal human body is in a hot environment or a cold environment, and the temperature of the human body is constant, so the heat dissipation of the two is equal to heat production. Because heat production increases when it is cold, heat dissipation in hot environment is less than that in cold environment, and D is wrong.

Therefore, choose: d.