What people need and should hear depends on the situation. When you visit a dentist, you don't need to hear about how to properly build a house, no matter how truthful it is. You should hear truth about state of your teeth. Or, if you are having a wedding speech, you should not pontificate about how to keep the bathroom clean - even if what you say is cold hard truth.

Second and importantly, it is not like these commencement speakers would be concerned with truth or were trying to convey truth in their speeches. The dilemma here is not "truth versus inspiration/delusion". Schmidt was not selling truth, he was selling his product and was trying to make people believe things that will make him earn more. Schmidt want trying to sell inspiring vision of the world for the students, he effectively put them into a passive-you-dont-matter role in his vision.