The best thing to do is use it as a learning experience. Talking negatively about his old boss or job will not allow him to learn from what happened. Talk about the situation that led to him being fired. I would make sure he knows what to do next time and help stay positive as he finds a new job.
Just to learn from his mistakes and experience, and build on it. He will experience many jobs in his lifetime, along with failures and disappointments. This is part of life, and it should only make him stronger.
Tell him that with todays economy that it is no big surprise that people are being laid off. To keep his chin up and be assured that things will get better. Time changes everything and with time he will have a much better opportunity and job. Tell him to use his time wisely.
