Think of it in these terms-do you know how far a 121 airliner can go without a f/o? Not even an inch, can't even run a cockpit clean-up checklist solo, because it's a challenge and response, requiring 2 pilots. I was a f/o for 6 years before upgrading, so I was always very keen on making sure I treated my first officers like i'd like to be treated.

As for the conduct of the jumpseater in question, his behavior was in-appropriate, and unprofessional, and so was your captains. Just consider that a learning opportunity and don't let anyone treat your co-pilot in that fashion when you sit the left seat.