I believe that forcing researchers to eat their own cooking whenever possible solves a serious problem in science. - Nassim Nicholas Taleb

Sometimes people ask you a question with their eyes begging you to not tell them the truth.

The only way we have left to control suicide-terrorists would be precisely to convince them that blowing themselves up is not the worst-case scenario for them, nor the end scenario at all. Making their families and loved ones bear a financial burden — just as Germans still pay for war crimes — would immediately add consequences to their actions. The penalty needs to be properly calibrated to be a true disincentive, without imparting any sense of heroism or martyrdom to the families in question.

If the professor is not capable of giving a class without preparation, don't attend.