aloha,
I think you're right on about "the art of conversation", I bet there is a book out there somewhere regarding that - if not there should be.
Some people do get offended by a strongly opionated person, especially in a first time engagement. In my opinion, most people have a tendancy to talk primarly about themselves, making it difficult (esp. if you have just met them) to continue or add to the topic at hand. I also think many people don't ask "why" or "what did you mean by that" or what does the word "blaptidityblob" mean. Sometimes people do talk to much, in turn, the listener may be overwhelmed with misunderstanding leading to the end of that conversation. Does that make sense?
So my resolve (just another opinion), is to reply by somewhat reiterated what the persons statement was with your interpreted value of what they ment, then followed by your opinion. If you feel maybe you have offended that person, it's good to ask straight up if they know what you mean. It's like righting a essay, start with the question, support the facts, then state your opinion. It's o.k. to disagree, as long you both know what you are in disagreement over. If you do but heads, it's nice to say "huh, I never thought about it that way".
Does that help at all?