this makes him look bad and the media will not let it go away
The fact that the dog had diahrea indicates to me he was scared. Most dogs love to be in the back of a pick up but probably not tied down to the top of the car in a small cage. Its possible that the dog could have been made to get used to it by taking him on small rides at first then longer and longer....each time giving the dog lots of comfort and affection after the ride.
This sort of reminds me of LBJ picking up his beagles by the ears....he got a lot of flak for that IIRC.