leave no man behind

i was wondered thinking why there are so many differences between people who belong to common race called humans.i found lot of differences like rich ,poor,black,white ,seperated by relegion,caste ,region ,................but to my foolishness what i beleive is behind every difference there is again a human brain.so it is we the so called humans one or the other way responsible for the well being or the worst being of the others . so leave no man behind . which i found or i think is very impractical.

note: i have a presentation made based on the above idea at the following link
http://www.slideshare.net/vsmkreddy/leave-no-man-behind