It is indeed unreasonable.

No animal evolved solely to produce food for humans and to be property, and I think that's a major blindspot that people have, which allows them to believe into this idea.

Buying an animal, restraining it in your property, subjecting it to whatever's needed for it to produce (look this up if you need to), consuming said products, and in the end of its useful life selling the animal (and let's not imagine that it's sold to animal sanctuaries): none of this is in line with being vegan. All of it harms the animal in some way and normalises the dismissal of animal life, independent of whatever the person wants to believe.

Someone who believes veganism is the right way, but is not personally vegan, can say just that: it's a perfectly tenable philosophical position to have. Self-identifying as vegan while not being vegan is where it becomes absurd.