Honestly dude the most respectful thing to do Is ask him when it comes to that kinda stuff it's always a preference thing. He might not want you to or he may want you too. For example when I start stuttering I prefer it when people finish what I'm saying however I've heard from other stutterers they don't like this; they like to finish though it. I say just ask the dude and be like "hey i would like to know if you prefer if i break eye contact when you stutter or not"