Sorry, did you even read the article? Let me highlight the relevant part that you apparently missed:
I’m also not impressed by arguments along the lines of “If everyone were vegan, that would actually be less eco-friendly than some amount of animal product consumption.” That’s like arguing that we need to discriminate against homosexuals because if everyone were gay, we’d have a problem.
Message from reality universe: that’s never going to happen. Even though the vegan community is actively recruiting people to their alternative lifestyle, they’re simply not going to convert everyone. I’d love to be proven wrong on this, and if we ever get anywhere near it, then we can start worrying about making sure that some people are still using some animal products.