It strikes me that a key strength you need to be a successful CEO of a major bank, especially in the current economic climate is good judgment*. Public whining about having to give up your bonus because of media and political pressure does not display good judgment in the current environment. Ergo, you are lacking one of the key strengths of a good CEO and you hence do not deserve a bonus.
I interviewed Stephen Hester once, I can't remember what for but it was before he was at RBS. Pretty much everyone I've ever interviewed has managed to be charming and polite, however stupid (or indeed to the point) my questioning. As I've said before, Fred Goodwin, even Fred Goodwin, was quite delightful. My abiding memory of Stephen Hester was that he was quite the most unpleasant, arrogant, rude man I'd ever spoken to.
*And I do not believe that this, along with the other requisite properties, is the sole preserve of a highly select few people.