My father was the King of Sarcasm. If people ever wanted to know from where I got it, they knew after spending a little bit of time with him. But it wasn't meant to be cruel. He always meant it in a light-hearted way and expected you to get it on an intellectual level.
Dad was also notorious for interjecting his opinion on everything. It didn't matter what the topic was. He would let you speak for a while and then had to insert his two cents' worth. Actually sometimes, it was more like two dollars' worth. The more he respected you and your intelligence, the more he had to say, sarcastically or seriously.
I think I got the brunt of that intellectual discourse when I was growing up. I am naturally argumentative. I prefer to think of it as debating. I used to pick up books on certain topics and memorize the information in them, just to piss him off and to spark debate. When I got older, I realized that we actually saw eye-to-eye on many hot topics. We just argued our points differently.
He and my sister also spend many hours debating intellectual design and other religious topics. He seemed to use less of that sarcasm with her, though. I guess I just bring it out in people.