Had a rather heated exchange earlier with a friend of my dsis.
This friend has apparently 'done a degree' in Autism, and was asking me some questions. I'd previously agreed to talk to him (I usually would avoid a social situation where I am the focus on pain of death)
I stated that in my family's case I believed it was a genetic cause.
Straight away he it seemed to me jumped down my throat and started to argue that actually he thought it was more likely to be certain factors during my pregnancy and that there are always multiple factors, never just genetic 
My dd has been diagnosed with ASD, as have I and my father, though we were diagnosed much later on in life. From stories we've heard about my granny (Df's mum) I would hazard a guess that she would have been too.
He kept trying to talk over me or to me like I was stupid so I got upset and left 
It's not even really that he disagreed with me, it was the way he did it.
AIBU in thinking that even if you have a degree in something you shouldn't start arguing about it with someone who is actually living it?