Natural Lactose Tolerance
There are a number of things right about Alicia's post. She's right to say lactose intolerance should be understood as a mismatch between a person's biology and the expectations of their society, not a deficiency in the lactose intolerant person. And the statistics she cites about the prevalence of lactose intolerance worldwide, and its particular concentration among people of color, is a good corrective to the idea that adult milk consumption is a human universal. So "everyone should drink milk!" has both ableist and ethnocentric components.
Where I disagree is her further claim, which she says tipped the balance for her in going vegan, that milk consumption is unnatural. In general, I don't find naturalness arguments compelling on their own, except as a rough indicator of potential problems when we lack other, more direct information (which is not the case here -- we have centuries of direct information on the effects of consuming milk). Further, I would argue that it's perfectly natural for European-descended people to be lactose-tolerant. European lactose tolerance isn't just a coincidence -- it's a product of evolution, a quintessentially natural process if ever there was one, fitting Europeans to better take advantage of the foods available in their cultural-economic environment (i.e., one with dairy cows). So absent further arguments about the harm to cows and the environment (which I think Alicia also accepts), those of us who are perfectly able to digest lactose as adults should be free to continue consuming milk.