Have you never negotiated anything? This isn't blackmail. He's leveraging an asset (his talents) for compensation. If Netflix is negotiating licensing rights to a movie and the owner of the rights says "We want more money or we won't license this to you." that's not blackmail. It's negotiating a deal. In this case the guy is saying "I want more money or I won't work for you any more."

It is absolutely the correct call. He was being taken advantage of. He used his only point of leverage to get a fairer deal.