It goes back to the dumbest possible conversation when a bunch of Nazis latched onto being able to digest milk as a sign of superiority. Why they still continue to latch on after being informed that the groups of humans on earth that can digest cow milk is incredibly diverse and very much not a "white" thing, well, Nazis are dipshits, so who knows.
Also I assume just the imagery of it being, well, white.
"They're coming for our cows!" narratives around climate change reactionary discussions.
I’m sure the Nazi angle and owning the vegans elements are a big part of it. But I also think it’s a coping mechanism thing where they try to spin their dorkiness as a manly, subversive transgression. They desperately want to be seen as revolutionary despite being the most bland, mayo on white bread people on the planet.
Even mayonnaise is too good for these people. These dudes have more of a miracle whip vibe. So tasteless they ruined societal perceptions of mayonnaise for multiple generations.
Milk is from COWS. The GLOBALISTS are trying to TAKE AWAY our sacred freedom by regulating COW FARTS!. I OWNED that COMMUNIST bar-IS-TA by ording a whole glass of COW MILK.
I think it's part of a white supremacist belief about lactose intolerance being a sign of genetic inferiority. There's been a few instances of groups of these dorks chugging milk in public as some sort of prideful act.