Why people act as apologists for other’s ideas?

I have seen this more than a few times and that does not make this one bit scientific. When discussing books with other, I usually find people are passionate about a recent book they read and quote profusely from it. Recently I was discussing childhood education with someone who wanted to make his case based on Malcolm Gladwell’s new book, The Outliers. I pointed out how Gladwell extrapolates (just like I do in this post based on random and isolated events) from isolated events and quotes research selectively without considering other studies that may contradict the research he is basing his results on.  Immediately my counterpart started defending the book, very politely I might add, even at the expense of ignoring our current task at hand.

If we identify ourselves with ideas and authors do we need to defend them or be an apologist for them as well? After all these are not our own ideas. May be we feel that someone arguing against the ideas are damaging our own belief system or even chastising our learning process. By defending the ideas we seek to re-establish status that we feel is being threatened.

What do you think?