Actually I'm going to expand on the steps of the pipeline.
"I want to do something to better the environment". A noble pursuit.
Then, "Large scale animal agriculture is bad for the environment". Accurate statement.
Then, "Therefore, I am going to stop consuming all animal products and biproducts." A lofty goal, but still reasonable. It's not something that's for everyone, but if that's what you want to do to do your part, more power to you.
Then, "If I can do it, so can you." Inaccurate. The human body is suited ideally for an omnivorous lifestyle. While the human body is very adaptable, its adaptability varies from person to person, and not everyone is able to subsist off of a vegan lifestyle.
Then, "People who don't follow my lifestyle are maliciously contributing to climate change." We're going into dangerous 'us vs. them' territory now. Now everyone who consumes animal products and biproducts even utilyzes large-scale animal agriculture, and there are myriad of reasons for someone to not be vegan. Personal lifestyle choices are also a distraction from the larger issue at hand, which is that corporations contribute the most to climate change, and blaming yourself and other individuals is a distraction.
Then, "Human beings are responsible for climate change. Humans are inherently destructive." False. Corporations and industrialization is responsible for climate change. Humans are inherently neutral, and for the most part are actually good.
Then, "If there were less people on this Earth, we would have less climate change and pollution." And there we are. At the ecofascism finish line.
Not every vegan ends up at the ecofascist finish line. Many vegans stay comfortably on the third rung of the ladder, focusing on their own personal boundaries and lifestyle choices. However, as soon as you dip your toes into the "if I can do it, so can you" mentality, that's when the ball begins rolling down the slippery slope of ecofascism.
As soon as you begin forcing your lifestyle onto other people, that's when it becomes dangerous.