When animals destroy the progeny or hard work of other animals to further their reproductive success, when they kill a competitor, or bond with other group members by killing individuals from an outside group, there does not seem to be a harmful effect on the general population and this may have also been true for pre-modern humans.
With modern humans, however, our survival is contingent on moving beyond the instability of being a society of extreme winners and losers and transcending tribal in-group out-group divisions. If we do not overcome these serious obstacles to global progress, we will likely lose our chance to solve the existential crises looming before us.
Fortunately, for masses of people to become as highly cooperative and social as necessary does not require us to swim against the current. We merely need to support the fullest expression of our naturally social nature. Presently, our mainstream culture elevates the importance of competition above all else — an emphasis that makes erroneous assumptions about nature in general and about humans in particular.
The unparalleled success of humankind directly results from our highly cooperative and intensely social nature. Lacking powerful jaws, sharp claws, super-fast speed, and formidable physical strength, but for our ultra-social nature, humans would have easily been overcome by predators before we ever made it out of the savannah from where we emerged.