Depends on the circumstance, were there people around, Proofreading is to save your boss from embarrassment, If you point out his mistakes in front of clients or other employees then it defeats the purpose of him asking you to proofread. If it was in private then disregard that last part and remind him that you are doing what was asked of you. Also I agree with #22

The internet.

That happens...he just doesn't want to admit it...

The Church of Scientology

The guy obviously has an inferiority complex a mile wide. Either he had some learning problems growing up or there's something else he's trying to make up for by pumping up his ego with his 'iq level'.

He should join the class that thinks Uncle Sam founded KFC.

Unless you corrected him in front of a whole bunch of people, I would argue that you're trying to prevent him from looking stupid by making sure he uses the right word. Spell check is great, but it won't catch people who write "your" when the proper word is "you're" or "form" when you mean "from" (a common typo I make but usually catch quickly). It's not as if he left the "l" out of "public" on something.

Nothing makes you smarter than misspelling college.

Stephen Hawking once said "People who boast about their IQ are losers"

If he doesn't want to be wrong, why is he making you proofread it in the first place?...