psychology would say that things are funny of they have a hint of truth to them.
blonde jokes (I'm blonde) are funny because you know a dumb blonde person or it would be without context
blonde jokes (I'm blonde) are funny because you know a dumb blonde person or it would be without context
"Eating rice cakes is like chewing on a foam coffee cup, only less filling."
This joke isn't literally true, but it is true that rice cakes are nasty and not very filling
+1 for blondes! (I'm one, too)
I don't think the humor in these jokes has anything to do with truth - they could apply to any group with a reputation for being dumb.
What's interesting is they probably would not be funny if Pole or blonde were just replaced with "idiot," probably because the listener doesn't get to make the logical leap to stupidity themselves. There may also be an element of shame and schadenfreude for picking on a group that adds to the humor.