Serious question.

How many of you are actually autistic?

Last night I went to a bro's. He ask me to bring my Wii for some PM. We all play Pokemon, so 3DS comes too. His younger brother is in his early 20 and is genuinely autistic. All night he is talking about Pokemon and strats. I offer to battle him and, aside from his Amoongus, I swept his team. He got quiet and paced around the kitchen and talked to himself for about an hour. Then he comes back and plays smash with us. He's decent, but he keeps talking loudly to himself and makes us all feel uncomfortable. My GF whispers that we should let him win. It comes down to just us and I kill him. He freaks out and runs upstairs and we can hear him yelling and stomping around in his room. Everyone looks at me like I'm a huge jerk.

Do any of you behave like this? Should I just let the guy win next time? I wasn't Being spiteful or mean, just playing like normal.