Hashim Amla is one of the best batsmen in the world at the moment, he is not a bowler by any stretch of the imagination, but he practices bowling and would be happy to pick up the ball whenever the captain will let him (but he knows that with the world class bowling attack South Africa has, he would rarely be a desirable bowling option). He is a team player and not a turd sandwich like Watson. However, someone of his ability, you could forgive for refusing to bowl. Watson, however, doesn't deserve a spot in a team he refuses to be a team player in.
Kallis has chronic back problems, yet still often bowls, again because he is not a turd sandwich and someone of his class would be entitled to do whatever they like. The point is Watson is a turd sandwich
insert Michael Clarke point with similar words to the Amla one, similar story goes for Hussey and any actual world class batsman. The point is Watson is a turd sandwich who does not deserve special treatment