In replying to a comment a moment ago, I had a bit of an epiphany on the fundamental difference between short term and long term thinking. If it's less than one human lifetime, it's short term. People who are fundamentally selfish cannot think outside the scope of their own lifespan, and thus are incapable of true long term planning.
Having humanity's best interests at heart means thinking beyond your own lifetime. That's where the long term begins.