No, they didn't. That's actually an example of 4chan getting busted for being white supremacists.
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The New York Times ran an article in September 2017 about how white supremacists misuse data about human genetics to perpetuate scientific racism. One very real genetic difference between different human populations is lactose tolerance, which is rare on most of the planet but common in Europe and thus in European settler countries. White Supremacists seized on this idea and were already using it in rhetoric and propaganda.
Several follow up articles (although not the PETA one) cited a /pol/ thread called "enter the milk zone", it's not some super secret psi ops operation. It's a sincere example of exactly what the New York Times article would talk about a few days later.
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PETAs article was not the result of secret 4chan meddling, it was PETA getting in on what was already a media event to push their own pro-vegan stance. The New York Times article's reference on milk primarily comes from a university lecturer who had gathered information on this trend as an example of scientific misuse to teach in a class, 4chan is not mentioned at all.
This is not a troll. I know it sounds like a troll because it's so ridiculous, but it's not. It's just that white supremacy is ridiculous. /Pol/ got caught out doing something white supremacists had already been doing for some time, and tried to spin it as "kek the libs think milk is nazi" by using PETA as a soft target.
When I say that these "trolls" and white supremacists are the same people, that is a very literal statement.