since they don't really have much diversity in their mostly-homogeneous society
That's what everyone who takes a glance at Japan thinks but it's not the case.
Not only are Japanese people an amalgamation of races themselves, but the number of 'halves' are increasing dramatically as are immigrants from places where Japanese migrated to in the past.
In fact, in some towns it's hard to find a non-Brazilian waiting at the train stop.
Despite what it likes to think about itself, Japan is a melting pot if not in racially, then most certainly culturally.
However, their 'insensitivity' is more linked to pure child-like ignorance. Take Bobby for example. Even though people realize and know he's a remarkably intelligent individual, he plays (or played) up the role of the doofus foreigner taken up by so many before him.
However, just because he's Black, Black people are complaining that he's playing up the sambo role.
WHAT THE HELL IS WRONG WITH THAT!?
If you read the original story (BASED IN INDIA) the character is quite intelligent and even gets rewarded for his quick-thinking. Some Americans once played up this fact and suddenly it destroys an innocent story? What the Hell???
The fact is, Akira Toriyama and others have taken up images that
we have assigned to be negative stereotypes. Did you ever think another culture just might possibly see the same thing a little bit differently? Believe me, if ever there was a rhetorical question...
Some Americans complain and whine to no end about how we impose our views on others, so then why are we doing it here as well? The character is seen as a humorous and above all, cute image. Who are we to dash in on a white horse and proclaim how they should view it?
Can the Japanese be racist? YES!!! Just listening to what some of my closest friends have to say about all Chinese people is quite....'fascinating'....I suppose is one word to describe it. But in recreating the sambo image, hatred and elitism is the furthest thing from their mind.