First of all I would have to say that's really harsh, both on the industry and the developer. He may have been a bit delusional and not thought the plan through but he learned why he was wrong and got better from it.
Calling game development "useless" is a stretch however, they have always combined math,art,computers,music,... into one single piece. They have also personally broguht me into the world of programming.
Saying writers don't have a purpose is also a bit over the top. Some can be reporters, others send ideas to people who otherwise wouldn't have even considered them.
Games are a firm example of entertainment, and people get joy out of seeing people loving their product. Can you honestly say you want to live your life without TV, movies, games, music, writing, art, stories, dance?