If I were your Captain, I would have noticed the jump-seater "dissing" you and corrected the situation. I would have done that by introducing him to you. "and this is Bob..." Disrespect my f/o and you disrespect me. Also, I would have made it a point to bring you into the conversation if the guy was ignoring you. Sounds like your captain was a bit of a jerk too. Did you mention this to him? Something like, "did you notice that guy didn't even acknowledge my existence?"

Having said all that, yes, there are many captains who look down their noses at f/o's.