An important part of Nazism was antisemitism. There is nothing antisemitic about Agenda 21.
Tables and old broom handles are similar in that they are both made of wood.
If you look long enough you can find some similarities between any two random things you dream up.
Why would anyone want to identify Agenda 21 with fertility cults or Nazism? Are people who are in favor of Agenda 21 or unaware of Agenda 21 going to say "Aha! This is the last straw. Now I'm finally going to oppose Agenda 21.
It would be as if someone thought that saying "Abortion clinics take up space in strip malls that could be filled with Chinese take-out places" would be the final nail in the coffin for abortion clinics.
This clip puts history into prospect.