That is naive. Humans are selfish, we need to accept this and adapt our poicies accordingly - as we have historically.
While I agree we aren't the nicest species of primate (that title goes to our cousins, the Bonobos), I also believe a lot of our nastiness can be attributed to nurture rather than nature.
My feeling is that any individual is OK with sacrifice as long as they are not unfairly disadvantaged relavitely to their society/neighbours.
For example: i would not be willing to pay more income tax unless this applied for everyone; even if i wanted higher income taxes.