I feel the methods talked about in this section will help when a student challenges you, I have practiced some of these tricks in the work setting and it does work. When a student is being difficult you don't want them to get you frustrated, it shows you are losing control of your emotions and you might say things as mentioned, the wrong way. Turn the class around and have them refocus on the lesson at hand being positive. 

Make sure the demo materials are ready so the students stay focused and don't lose interest.  Put variety in the lesson so it is not all lecture in one class period.

This is another part of preparation to start the class out right, introductions from the instructor tells his or her experience and also introductions from the students to know thier past experience or goals.

Plan and prepare for the class so the students recieve the best experience.

You need to be a leader, mentor and show the students how to be respectfull for each other and professional about it.