I wouldn’t consider this a failure. He tackled the presentation head-on and made zero excuses. I know you mean well but I don’t think this “stuttering = failure” mentality is helpful. I consider avoidance a failure. He did not avoid this. He faced his fears. He was victorious in my book. However, I do agree with your advice of being able to laugh at yourself if you stuttered a lot and to keep a strong head and keep moving forward.