Leftist have a long history of violence, assaults and vandalism. They also have a longer history of hijacking agendas, and rewriting history. So Gaylord had heard of the idea from McConnell, and he like it and the branding -- but his idea was different. Instead of just a day, what if “Earth Day” is a massive, world-wide “teach-in” where the masses will be taught what the progressivist educators want you to know?
What's a teach in? - during the 60's, some anti-American Marxists were fueling the perpetual outrage, and were supporting violent protests agains the establishment, Vietnam war, racial inequality, and so on. It was part of cultural Marxism and post modernism. In 1965, UC Berkley Academics decided to have a more peaceful "teach-in" -- where instead of violent protests, all the protestors would go to a cult meeting, and academics could teach them alternate-History as a means of indoctrinating anyone who cared to listen. Basically just chat about how America was an imperialist nation, and converse about why communism really wasn’t such a bad form of government, until you got the herd correctly aligned (and attacking anyone who disagreed). It helped the perception of the movement as violent, and deepened the followers commitment to the cause: it was a protest and Church of Anti-Capitlism sermon in one.
Later, Nelson's defenders claimed that the John Birch Society just invented the Lenin birthday thing (complete coincidence), but they never explained why he was adamant to move the day from March, and picked that day in April. Marxists may fail at economics, history, compassion, tolerance, liberty and a few dozen other things -- but they excel at virtue signaling and taking credit for other people's inventions.
And he changed it from just a Holiday for people to reflect -- to one with speeches, rally's, riots, lectures, and general Marxist revisionism.
Gaylord is often credited with being the founder, and John McConnell is often forgotten by history as the creator of Earth Day. Bill Clinton presented Nelson with a Presidential Medal of Freedom in 1995 for his efforts, as have lefty violence supporters from all over the globe.
useful idiots, to refer to pawns and sock-puppets, working as paid (or unpaid) supporters of the Soviet Agenda: sometimes knowingly, and sometimes not. While many things John McConnell did, might have been somewhat helpful to the Soviets agendas, Gaylord Nelson was the epitome of what they were striving for: brash, gullible, communist sympathizer, stupid, environmentalist. What's not to love? His Daughter Tia Nelson proved that nuts don't fall far from the tree: she was Wisconsin’s public lands administrator until censured and drive out for talking about Climate Change too much, and annoying everyone. Tia Nelson: http://host.madison.com/wsj/news/local/environment/months-after-climate-change-gag-earth-day-founder-s-daughter/article_040be7eb-3a91-502c-8834-90840b9c1a93.html</ref>
As was common at the time, Gaylord's anti-population, pro-Malthusian views, lead him into racism, pro-abortion, anti-immigration and eugenics. Which while popular with the left of the time, is something the left of today would rather gloss over.... especially the anti-immigration part. So they either ignore, context, or distract from quotes like the following:
❝ As far as I know, most organizations are avoiding population issues because they're politically frightened by the charge that comes from some proponents of immigration that if you oppose the immigration policy we have now, you're a racist. There is no way in the world we can forge a sustainable society without stabilizing the population. ... There's no practical way of stabilizing the population of the U.S. without reducing the immigration rate. ❞
Other racist and anti-immigration or pro-nationalist groups (like VDare) all support that more racist/nationalist/anti-immigration side of the leftist movement. While the left all hand-wave and try to pretend that all racist movements come from the right side of the aisle.