Read Laureano's own words for a different perspective instead of taking the (Communist-sympathizing) Star Tribune and its reporter's report at face value.
See https://mannylaureano.com/2017/12/05/so-how-was-your-day-a-summation/
Claims that he did a cursory look at who Wainright was ahead of the concert, but did not come across the depth of the guy's hatred for Trump and the GOP. He also claims that he did not 'gesticulate' or 'storm off stage', rather he walked off stage after putting away his instrument, and on the way ut informed the second chair that they would need to fill in for him.
Also read the Powerline Blog article where I first read about this story, for other commentary.
The quote should have read, I understand the trumpeters disgust, but that was the wrong time to express his disagreement with the entertainer. The trumpeter should already have known. Wainright has been talking this way in public for many years. Manny may find it more difficult to get work on this level for a while.