But differences are there and they are obvious.
Are they?
This is a debate related to evolution. In some area humans had simple survival, while in other regions they had to work hard, physically and mentally, to survive. This evolved us in slightly different ways.
Human survival has never been a simple task in any part of the world.
Humans are highly adaptable. There are many different environments people have lived in, each one presenting some different challenges to survival. That is one reason for physical differences. There is skin pigmentation, resistance to certain diseases and susceptibility to others, prevalence of types of hair etc.. Negligible or superficial stuff. In all important ways people are the same everywhere, and they do the same things.
There is, again, no demonstrated difference in intelligence (or behavioural traits, for that matter), the heritability of which is itself not clearly understood/is far from established.
The other day I saw an NHS advert on a tube station. If you are arain or black, and over 40, you have x times more chances of having type 2 diabetes (or 1, i dont remember).
Shall we sue NHS for this advert???
No. Although the causes of diabetes aren't well understood and they correlate with loads of different things.
We are slightly different, physically and mentally.
Everyone is slightly different physically. A given group of people identified in any millions of ways are slightly different to another group of people identified in another way, and so on. We can't be placed in distinct categories on the basis of such differences. We have 99.99999% more in common than we differ from a biological POV. Take a child from Solomon Islands to New York and they'll become a complete New Yorker, along with the styles of dress, taste in food, tendency to obesity, etc..
As different as people are mentally, for all kinds of reasons, southern africans aren't thick as bricks and asians are as likely to be geniuses as anyone else.