You are right the hiring managers can be idiots.  This story reminded me of an interview I took just after graduating from college.  I was asked a question by 1 member of the group interviewing me, I answered it and then the "manager" asked me the same damn question only worded different.  I paused for a moment and looked around at the group and didn't see any reaction in anybodys faces so I proceeded to answer the question again.  I got the job but after 3 1/2 years I couldn't stand working for a manager who knew all the buzz words, but nothing else.

I've been on the other end too though, and have been asked a question about something I knew but it just wouldn't come out at that moment.