Lots of builders are set in their ways and resistant to change. I've been guilty of that myself in building engines for customers, although I never go so far as to actually bash their preferance, but at times I did insist that if I built it I would use xxx brand or I would not be interested in building it. To go as far as he did sounds pretty unprofessional to me, but it's his business and not mine.

As to the barrel issue, he's just tyring to push a sale on you.