Professor smith told one class that alcohol consumption has been found to increase sexual desire. He informed another class that alcohol consumption has been found to reduce sexual appetite. The fact that neither class was surprised by the information they received best illustrates the power of

I believe the answer is: hindsight bias

hindsight bias refers to a false perception that make people believe that they knew a certain information all along without even checking its validity. This tend to happen when people receive the information from the person that they acknowledge as an authority or extremely competent.