Because you have a short attention span and base major decisions on how sharp the person talking about them looks and sounds? Oh and the fact that you've already made your mind up before they've even opened their mouth.
It's amazing how people read into what others say. There was no implication about my attention span. The man is childish and arrogant and he has demonstrated this repeatedly.
It's not out of the line of reason whatsoever to be predisposed to an opinion if prior behavioural patterns show certain qualities. So, yes, largely my mind was already made up - based on other times I've seen how he behaves. It's not that much of an intellectual jump to see why this is reasonable.
He's not always wrong or he wouldn't be where he is today. I just don't like his attitude.