well I'll let you in on a secret. A lot of men are dumb for the same reason blondes are. It's a good way to make people feel sorry for you and you get out of having to do stuff you don't want to.
Example: You don't want to do the dishes? Do them really bad just once. Leave food on them. The woman usually can't believe how bad the man is at dishes so she just does them herself b/c it's easier.
The other reason we are dumb is b/c we don't think before we open our mouths. I'm a prime example of this. I got lucky by finding a woman that can sympathize with my stupidity. I've said stupid stupid stuff to her in the past and yet she still loves me for some reason.
But give us some credit. Afterall, we were cavemen at one time!