I'm also an advocate of de-populating the planet. That's not inherently a bad thing. This planet cannot sustain an infinitely growing population - If not by resources then by room! Eventually you will have to reduce population to a sustainable level.
There are ethical ways to do this. Most educated rich countries tend to have sub-replacement fertility rates which is fantastic news! It suggests you may be able to create a sustainable planet by improving the education and economy of third world countries!
If you want more insight into Bill Gates I would highly recommend the three part documentary 'Inside Bill's Brain'