not an expert)
I think its referring to the whole "we are one people" idea that Christianity initially touted. that we are all the products of "God" and therefore should be good to each other.
"the whole Earth was of one language, and of one speech" probably referrs to the shared ideas of man (a "universal language" in the form of things like philosophy, religion, or hard facts like math or science.)
TLDR; Human is Human. be good to Human you f**king idiot.