To my fellow teachers:
There’s nothing wrong when a student gives you some counter-arguments in your discussion. There’s nothing wrong when a student corrects your statement/presentation/grammar (I thank him/her for that, too).
It means that they are engaged in class. It means that they’ve seen another angle in the material. It’s actually a sign that there’s going to be a healthy discussion, and it’s one of the things that we, as educators, should always look for in class.
When a student disagrees, listen carefully to his or her statement[s]. Look at the bigger picture. If you can’t give a reply at that particular moment, let the question or argument linger for a bit. Think about it. Write about it. Dream about it. Ask people about it. Discuss it with friends over dinner. Don’t just dismiss the student’s perspective (or their character) and accuse them of being know-it-alls. Don’t you dare smart-shame them in front of everyone.
Remember: students are human beings, not programmable mindless automatons.