Read the comments....only a dimwit teacher would think that this is appropriate. Also, you did not address my major point and that was if this is legal under the law what would stop them from a demonstration on how to snort coke.
sex is not illegal. Cocaine is.
And I dealt with a key factor of your claim that a university classroom is a public place. It is not.
Stand up for what is right, even if you have to stand alone.