Why, older men....?

Why is it that whenever I meet a charming, sexy, macho older guy that I like, he gets sensitive whenever I know something he doesn't and tends to pull back? It's not like I beat people over the head with literary stuff--I just mention things as they happen to come up.

I'm asking this question because it seems that most of the men my age and younger seem totally cool with demonstrating complete ignorance of any and every subject. Even (most of) my colleagues aren't embarrassed if they don't know something, and they're in my discipline (English Studies).

It just seems like the sexy "Bruce Willis" type just doesn't like it if a girl is attractive and also well versed in an area he hasn't studied that much or that long. :(

Update: August 01, 2007.
Someone please C-Star pandorasfault. Really great answer. Thanks.

Update: July 31, 2007.
bailaren, what do you think "mention things AS THEY COME UP"(emphasis added) means? Geez. Some people have inadequate male type problems. :(