Hello! Stuttering is primarily a neurophysiological disorder. It is NOT caused by him not knowing what to say or him needing tho think about it first. The fact he is talking and stuttering without caring is a blessing. Many people who stutter become extremely shy, self conscious, and have significant anxiety and shame about talking. This friend of yours clearly is amazing and does not give a damn about his stutter. His stuttering is a communication difference. Treat him like any other human. Let him finish his sentence, don’t interrupt, and be a good friend. If his stuttering annoys you, then maybe, just maybe you do not need to be friends with this guy. Don’t become the problem. Don’t be the person to mess up his mental health about his stuttering. (Source: I am a speech pathologist and a person who stutters)