Eh, I (natural blonde) was never offended by these jokes.

One of my favourites:

A blonde is driving down the motorway when she spots another blonde in a boat in a wheat field, rowing with all her might but getting nowhere. Angered by the situation, she pulls over to give her a piece of her mind.
‘You idiot!’ she shouts. ‘You’re giving all us blondes a bad name! If I could swim, I’d come out there and kick your arse!’