I agree, sometimes it is good to have other ideas and questioning of things. I agree it isn't good to just accept everyone's statement as fact. So I can appreciate his skeptism also, especially if it doesn't rise to the personal attack level but remains objective as much as possible.
Let's face it, we've all been wrong before, and all thought we knew something when we didn't. Others with different viewpoints can sometimes help us figure out things. Other times of course it isn't constructive. But believing everything we read in books, or the latest health fad for this or that, well, it can get expensive or be a waste of some good years of life.
So healthy skepticsm, I'm all for it (until he disagrees with me--just kidding).