People do this all the time in the professional world. Its no different than the guy who is mentally checked out and looking for a new job. Or the guy who sees no path to advancement and starts looking for new opportunities. He made a business decision that may work out, that may not. If he wants to come back, it's up to him to reconcile with his teammates and nunzio.
During the course of my "short" career to date spanning three companies and four client agencies, I don't ever recall leaving any company or agency project without providing a minimum two weeks' notice, as well as full cooperation in assisting with continuing project work as well as orderly transition/training of personnel. What Blackshear did is way more analogous to one telling their project team/manager that they have decided to sit out of a major presentation to management/executives that they have a managerial or otherwise instrumental role in on a couple of hours prior to, because said individual doesn't like managerial decisions during a down fiscal/business year. On top of that, the noted individual shows up to every major presentation/demonstration thereafter all suited up, but just watches as their project team struggles unsuccessfully with execution/demonstration/etc. without their assistance.
Before people chime in with claims that Blackshear is a college student figuring things out, I never "quit" or sat out a group project/presentation at Rutgers Undergrad and Graduate schools for any reason. In fact, I attended a family member's funeral one weekday morning in Queens, then drove to New Brunswick during afternoon rush hour just to participate in a group presentation because I felt responsible for my contributions, whether major or not. In this particular situation, quitting or putting in for an immediate transfer from the team/company altogether due to health, family, or other personal reasons would have arguably been more understandable.