A big problem I see here is that this: Is NOT EVEN CLOSE to the same question as this: Which is not the same as this: But you apparently can not tell that they are not the same thing. Let me ask you... Do you think the world would be better if all of us were black?
Do you think the world would be better if all of us were Negroes (as opposed to the precise color of one's skin - black, brown, tan, etc.)? How would you visualize such a world compared to the present one?
Nope, diversity is our strength so we should do all we can to preserve our diversity, to become all one color would weaken the human race.
The catch-22 of that is that in order to take advantage of racial diversity to "strengthen" the human race, the different races would have to interbreed - thusly moving us towards homogeny. If you are talking about "strengthening" the human race, diversity is not how it would be done. When people refer to diversity being our strength, they are referring to "pure breeds" having negative traits (i.e. susceptibility to certain diseases) being common among the breed - just like dogs. If we were all mutts, the strongest traits could be selected for from a larger pool, and the weakest traits would be bred out.