To wit, proposing that the western economies/cultures most able to continue their existing work in making more efficient use of energy "fix" the problem by crippling the very economic engines that produce the largesse that funds that sort of R&D... while leaving 50% of the world's energy consumers to merrily (and with vastly, vastly more polluting inefficiencies) keep growing and burning as if they were still some small village... that's the perfect scenario in which to apply a princple of caution.
If you put it this way, it does sound bad; but consider your presuppositions.
I see no reason to conclude that reducing CO2 emissions will necessarily lead to the "crippling" of western economies. If anything, the current capitalist system requires that people (marketing people, mostly) continue to invent reasons why we need to get rid of old technology and buy new stuff- this enforced obsolescence, after all, is what keeps the economy, as it is currently structured, going. So why would new regulations that spur both technological innovation (in renewable energy) and enforced obsolescence (new environmental standards forcing old inefficient plants to shut) be bad?
As for your claim that we in the West should "buy some Brazilian village a new bus", this is precisely what the carbon trading scheme in Kyoto is designed to do. Countries like Germany, where even fossil fuel powered plants are pretty efficient, can essentially buy their way to increased pollution by offsetting pollution in, say, China through building a more efficient power plant there.
The point about the fact that India, China, etc are excluded from Kyoto in any meaningful way is well taken. Of course developing nations need to rein in their emissions (assuming that our goal is to reduce CO2 emissions), but the only way that can happen is if the West lets them use new technology rather than forcing them to develop along the same dirty, polluting course the West took. And there's the rub, because that involves the West licensing new technology at prices that are affordable for a low GDP country.