I am opposed to the implementation of this exercise, I believe its basic concept seriously undercuts the moral lesson we should take from Petrov Day.
The best way to not blow ourselves up is to not make nuclear weapons. On a day dedicated to not blowing ourselves up, LW has decided to manufacture a bunch of completely unneeded nuclear weapons, hand them out to many people, and then hope really hard that no one uses them. This is like a recovering addict carrying drugs on his person in order to make a point about resisting temptation: he is at best bragging and at worst courting disaster so boldly that one should wonder if he really wants to avoid self-destruction. This makes a good allegory for the senseless near-apocalypse of the Cold War, but deliberately creating a senseless risk does not seem like an appropriate way of celebrating the time we narrowly avoided triggering a senseless risk.
The other reason vegan advocates should care about the truth is that if you keep lying, people will notice and stop trusting you. Case in point, I am not a vegan and I would describe my epistemic status as “not really open to persuasion” because I long ago noticed exactly the dynamics this post describes and concluded that I would be a fool to believe anything a vegan advocate told me. I could rigorously check every fact presented but that takes forever, I’d rather just keep eating meat and spend my time in an epistemic environment that hasn’t declared war on me.