I don't understand why you think this is some conspiracy. I haven't read anywhere, anywhere that it's left side. All I've read is that it has no party affiliations.
So why did you refer to it as "socialism" in your OP? Socialism is fairly synonymous with the left. As for it not having any party affiliations, no, it doesn't. But the criticism of Agenda 21 is almost entirely based in the Republican fringe, especially the 'Tea Party' movement.
I've also read about it being implemented. I personally know one of the MA Republican delegates showing me where and how it's being implemented in my area, and showing me copies of some of the paperwork with the words, very distinct, "sustainable development," that have been handed down from "governmental," but not government, bodies. Arizona has opted out of it.
First of all, what is wrong with implementing sustainable development policies? Of course sustainable development policies are being implemented. That is because prior urban planning policies were unsustainable. We cannot have continuous urban sprawl, because it is environmentally and economically disastrous.
Secondly, you seem to have bought the idea that because the Agenda 21 conspiracy theorists say Agenda 21 is a plot to destroy private property under the guise of sustainable development, anything to do with sustainable development must therefore be part of the Agenda 21 conspiracy. There are two problems with this:
1) The Agenda 21 conspiracy theory is derptarded - it does not exist
2) Even if it DID exist, the above is a massive
non sequitur. Just because A-21 calls all its evil plans 'sustainable development', does not mean that all sustainable development plans are part of the conspiracy.
Seriously, this is crazy, looper stuff. Even the Republican establishment is embarrassed by it. They were mortified when it got onto the party platform.