I remember hearing about agenda 21 years ago when i read more conspiracy theories - when i actually got round to reading some of it i couldn't believe how innocuous it all sounded, just some vague positive sounding aspirational waffle about sustainability with nothing actionable behind it - which on the american conspiracy right of the time was portrayed as tantamount to communism (communist=un angle is unsurprising as some of the conspiracy theorists saying that stuff derived directly from earlier john birch society nonsense (i'm thinking alex jones in particular)).