SAF, I don't think anyone is under the misconception that a black actor would only be, "Talking jive and running around with a boom box." We've all seen classy, intelligent, dignified black characters hundreds of times over. Elba could easily play that type of role.
But being white IS a fundamental part of Bond's family history. Unfortunately, his history is one that a black man would be extremely unlikely to have, even in the UK. I don't like that fact, I think it stinks and we've got a long way to go as a race (the HUMAN race), but we're making progress. But our upbringing and our youth largely defines who we are. Bond comes from a background that has made him who he is. He doesn't have that fundamental distrust of white people that most black people understandably have to one degree or another. There are some real mean spirited bigots out there that treat black people like crap. There are also some stealth bigots who treat black people like crap in subtle ways that most whites wouldn't notice, but a young black man would be very aware of. That creates a little resentment, a lack of trust, and feelings that James Bond has never had in any form. It would be a fundamental change in his character. He would no longer be the same James Bond that we've all known and loved for decades.
Ian Fleming described Bond's appearance, and he wasn't the least bit black. James Bond has always been a white man in the movies, keeping in line with who James Bond is in the novels. People don't just spontaneously change ethnicities (outside of Michael Jackson, anyway). Changing Bond's ethnicity WOULD be changing the character in a fundamental way.
This topic came up several years ago when some people wanted Colin Salmon to take over as 007. It was a bad idea then, and it's a bad idea now.
As I said then, I'll say again now - I would LOVE to see a Bond spin-off with Elba playing 009. That would be VERY cool, and it would allow EON and their production partners to put out a movie every other year at least. They would have greater revenues, so it would be a total positive. AND it would create a NEW, EXCITING superspy who just happens to be black. That should be the goal - to create a new iconic character that has some color to him rather than trying to retcon a white iconic character and make him black for PC & PR reasons (the absolute worst reasons to make that kind of change).
YES, casting a black actor to play Bond would get HUGE coverage in the media, but then what? What if the movie flopped? Or what if the 2nd movie witha that actor flopped after the novelty wore off? Would the story then become, "BOND FANS ARE RACISTS"? And what about recasting once Elba (or any black actor) left the role? Can you imagine the cries of, "RACISM," if they recast a white actor back in the role? Think about it, EON would be painting themselves into a corner by casting a black actor in the role, potentially ending the series if the public didn't accept a Black Bond. They'd have to wait a decade or so and reboot again to get away with casting a white actor in the role after a black actor played Bond. As a Bond fan I don't want to wait 8 or 10 years between Bond movies. The five year wait from LTK to GE was far too long for me. Waiting even longer would be really bad.
I still maintain that a NEW Double-00 played by Elba or someone like that would be a win/win for everyone involved. EON gets a 2nd property, and the world gets a new iconic character that just happens to be black. Awesome for everyone. Isn't that preferable?