Well, maybe, and maybe not. The presumption is that he has capacity unless established otherwise. And adults with capacity get to refuse care for whatever damnfool reason they like.
I agree a formal capacity assessment (and the doctor having a bit of space to talk things through with their patient without Mr Shouty there) would be prudent.
Unfortunately I can't get the video to play, so am aware that I'm speaking without a full picture. I guess I'm just making the point that the fact that he will die without care isn't a reason to keep him there against his will, if he has the capacity to make that decision.