Yeah, because we'd all have loved TLJ if Mark hadn't been so visible frustrated with it
He wasn't unprofessional at all, that movie was diabolical and Star Wars is obviously a huge part of his life, he had difficulty hiding his emotions which is understandable. Compared to how many people might have acted in his position, he seemed fairly dignified and restrained. And he's right about that being a badass image. Doesn't change his overall character ark in that movie however which was disappointing. You could easily argue that he's being a good employee and trying to find silver linings in a bad apple. Hopefully his positivity is due to him knowing (and liking) what's going on with the next movie.