Seriously though, why does James Bond have to be white?

I personally don't think it does, but I would say the same about Superman (who you put on a list of characters who you would preserve the ethnicity of).

For me, his masculinity, his disdain, his wit, his Britishness, his masculinity, and his balance of brute and gentleman are intrinsic to the character, but not necessarily his skin tone.

For the counter-argument:

Fleming, the original author, envisioned him with certain characteristics. One of those was race (slightly altered to be of Scottish descent after Connery impressed Fleming). I do also believe that it's important to maintain the vision of the creator, in this case, Fleming. Just because it isn't important or apparent to us why Fleming chose certain traits, well, that doesn't matter so much as upholding the character.

Also, if we want to characters to suit our sensibilities and reflect our ideals/times, why are we altering past characters of other people's sensibilities to suit our needs? Why not make new characters?

Finally, look at this from the counter-argument: Bond is a set of attributes and that set includes white. The character works as-is. Why change it?

It no longer matters. I have seen all the films and I love most of them. But I also love the original character of Bond as the conflicted cold warrior fighting Soviet agents and eventually the sort of characters we now identify as Bond villains... In the books. There was a continuity in the books and some of the recent novels by other writers carry on that continuity. This is set in a recognizable historical context - Bond would stick out ridiculously as a black man in that setting but that setting is unique and separate. It will survive as text and maybe someday there will be "retro - Bond" video series set in period and incorporating a version of Fleming's chronology. Or maybe not. I can get along without it.
The films are two or several (depending on how you look at them) discontinuous series that some people are so wrapped up in that they devise ideas like the "codename" theory to maintain some sort of poorly thought out canon. But Bond in the films is any actor and any variation on the elements that the public will accept. Literally the only reason Bond needs to be a white man in the films is that changing that will affect sales. Who knows how long that will last.

People outside the UK still consider it a majority white country... Foreigners would be the first to laugh at the idea of a Black (or indian, or chinese descent) James Bond... Why not have an Italian or Spanish actor play him? lol

It just wouldn't be James Bond... It would be someone else...

It's more likely that casting Idriss Elba would work as a star of a Mission Impossible movie then it would as James Bond.

I could see them continuing the franchise in another direction, by introducing new agent characters (of different stripes), or with spin-offs... and they're already making Bond more of a team player (mission impossible style)... less flirty... but that would just be seen as a modern interpretation... the essence of James Bond is set in history... in the novels and the initial movies...

But Bond will always be a White English guy... Even with Sean Connery's thick Scottish accent people still see him as some English bloke, with a license to kill who thinks the world is his oyster... with all of the fun and baggage that that brings...

"... guys like Luke Cage and Black Panther have to be black because that's their character..."

Oh really? Why exactly does Luke Cage have to be black? There are no poor white guys (or girls) who grew up in a ghetto? It's inconceivable that a white guy with Cage's powers would hire out his heroism? I don't see one credible argument that Cage, in particular, needs to be black. You just state it as a given, as if it's completely incontestable. I say you're wrong. I suspect the only reason you think Cage must be black is because he felt the sting of oppression as you conceive of it as being experienced by black Americans, and because he talks the jive vernacular that's more characteristic of black Americans than anyone else. If Bond's personality and persona can be changed to a different race, then so too can Cage's by the exact same reasoning. Even a white Black Panther could be written as a racial anomaly in Africa. Maybe you haven't noticed, but the entire population of Africa isn't black.

I'll expand even further on your question. Why does he have to be a white British officer? The inspiration for James Bond wasn't even Western European but an Eastern Slavic Serbian.

Same question goes about the Ancient Greek portrayals in Hollywood movies. Both "Alexander" and "300" primarily used actors of Northern European descent when in reality the ancient Greeks looked at people like Gerard Butler and Lena Headley as barbarians.

Seriously, though, why does Kunta Kinte have to be black.

Rationalize the F out of that. I'm sure you will.

I have no problem with James Bond being non-white. All I ask is they find someone who can act (no more Artemis Fowl misfires please).