> Less demand for resources, and consequently less damage to the environment?

While this is intuitive, it is largely incorrect. As our population has increased, we have become more efficient due to network effects. With a decreasing population, you'll experience a reduction in efficiency.

Also, at what point will you be satisfied? Ideally, with humanity extinct, we'll be using zero resources and won't be damaging the environment at all. That's the definition of misanthropy, isn't it?

> As our population has increased, we have become more efficient

The efficiencies that we've gained hasn't kept up with population growth. If it did, we wouldn't be having major issues with things like climate change, over fishing, or water shortages. Moreover, if you've read one of Bill Gates' more recent blog posts; gaining efficiencies doesn't lessen demand for resources.

http://www.gatesnotes.com/Books/Making-the-Modern-World

> Also, at what point will you be satisfied? Ideally, with humanity extinct,

Please re-read the post that I replied to. I was just merely giving an answer to a question: "Why is a smaller population a good thing?" You're making too many assumptions with too little data.