He's Radagast the Brown, not Radagast the Crappy. He's not a bumbling moron, and he doesn't have a stupid warg-chase-enabling rabbit-sled. (Stupid Warg Chase post to follow.) He's a proper wizard like the others and he doesn't deserve this treatment.
And he doesn't have BIRD POO in his HAIR.
(I feel I've waited long enough on this movie, so if you haven't seen it, stop reading for a couple of weeks; alternatively, chortle to yourself as I seem even more unbalanced than usual.)