Who knows what he thought, but I'll bet he interpretted the exclamation marks in your response to mean that you were mad, and you're right he lost his cool before you, but your response made him decide it was easier to brush you off than deal with you (if he was legit).  When it comes to parts sales many sellers don't really see it as a business (i.e. "the customer is always right") they see it as doing the community a favour.  So in a sense because they have what you want, they get to be pricks and you have to "play nice" to gain favour.  It seems to be the law the jungle out there.  It's also understandable that you don't want to be ripped off.