I don't think we can blame poor Hayden.
It would take an actor of genius to make those lines sound compelling in a film without cartoon characters darting in and out of frame every two minutes.
Ahmed however should have recognised the classic Stepin Fetchit routines when he read them.
If Brian Blessed had played Jar-Jar and he had played Boss Nass it would have still been silly but it wouldn't have been so darned uncomfortable to listen to.