That's kind of apples and oranges. For better or worse, the character of Tonto is defined by his Native American heritage. His characterization, speech patterns, and name are all defined by his race (which can probably be viewed as inherently racist, but that's another discussion). Ford's race is only defined as being an alien in disguise, which opens the doors up to just about anything.
Okay, I guess I didn't see the difference because I've been (and still are) utterly clueless about this 'Lone Ranger'. Was it a real person? I also somehow missed that the discussion wasn't about the Lone Ranger but about 'Tonto' (whoever that is...).
Now, if you tried to make Arthur Dent an American, I bet there would have been a bit of an uproar in the HHGTTG fandom.
Exactly! That's what my next question would have been: "How would have felt if Mos Def had played Arthur Dent instead?"
Anyway, I don't feel the objections against Johnny Depp playing the part of Tonto are well-reasoned. While it may be preferable to pick an actor with a matching ethnic background for a role, ultimately all that is important is if she's believable and playing the part well.
Does every Japanese have to played by a Japanese, every German by a German? Of course not!
Personally, I care more about the voice than the actual looks. "Sherlock Holmes" with an American accent just feels wrong to me. Likewise I hate exaggerated accents, e.g. when actors portrait a French.
"Van Helsing" was utterly terrible and I couldn't stand to watch it in the original because of the fake Romanian accents (not that the movie was particularly good in any other regard...).
There are actors that are good at speaking with different accents, e.g. Hugh Laurie as Dr. Gregory House.
Similarly, it would of course be preferable if every movie was filmed on location. It's rarely done because it's often prohibitively expensive. And in the end it doesn't matter all that much if the audience doesn't realize it's not the real place.
Now, back to Johnny Depp: Did you see him in "Fear and Loathing in Las Vegas"? Why did they pick him for that role? Couldn't they have saved a lot of budget for the make-up if they'd picked someone that looked closer to what they wanted the character to look like?
Maybe they picked him because he was actually the best actor for the role the audition?
Would it have made a difference if they'd cast Johnny Depp for the role of Tonto before his breakthrough and being recognized as a first league actor?