Besides, its a perfectly legitimate question, with a perfectly legitimate answer.
I'm trying to find out how smart people THINK they are, not how smart they ACTUALLY are. Not only is it more legitimate, it tells you more about the person. And to a certain extent, it is more verifiable.
And if you had carefully read my original post, with all its included and implied caveats, you might have noticed how I actually anticipated and answered your objections.