It's not at all selfish. It's not like burning the Juubi and the Bijuu gives Sasuke some kind of thrill, the Bijuu are part of the problem. Humans clearly don't know how to handle living with the Bijuu as very few have actually coexisted with them. Sasuke is doing things on a need-to-do basis.
Think of it this way, the Bijuu are nuclear weapons. The weapons are made to intimidate, if a nation has it, no one wants to fight because then they'll use it and blow others away. But then everyone wants one, and starts getting their own. Now that there are so many, people are no longer afraid to fight because they have their own, they are now willing to fight, eliminating peace.
The Bijuu are similar, how can people fight and cause chaos with weapons of mass destruction if there are no weapons of mass destruction?
The needs of millions of people outweigh the needs of 9 creatures.