As I understand it, the principal objection to the Hamilton actor's lecture to the VP-elect, was that he was singled out without warning in an attempt to embarrass him.  Many in the audience thought this was fine or great but some that were asked, thought it was inappropriate because they paid to see a show, not a lecture.  Imagine President Obama, attending a country music concert and at the end, the artist lectures President Obama about the 2nd Amendment.  Even though the message is appropriate, that would not be the time to deliver it.  Plus it's pretty rude.