I have nothing against Vegans. Sure they're the butt of everyone's jokes, but that's not really because of their lifestyle, just their superior, holier-than-thou attitude about how everyone else in the world is evil for eating fish and chicken. If you want to be Vegan, more power to you! I'm sure you can lead a healthy lifestyle and there are plenty of people who have proven they can, due to human biology.
Dog biology, however, is very different. And it pisses me off to think that some Vegans force their lifestyle on pets who are carnivorous by nature.
Like this person who posted a sad looking picture of her dog on Tumblr, boasting about how happy they are to eat the vegan meal they prepared. The owner wrote, "On the menu for Maggie tonight is puréed sweet potato, puréed brown rice, sprouted organic tofu, chia seeds, and digestive enzymes. Does she look excited? She is!"
Then someone laid down some biology expertise, breaking down everything wrong with this dog's "healthy" meal. They started by saying, "This dog does not look excited, this dog looks malnourished."
Another commenter tried providing anecdotal experience about vegan and vegetarian dogs enjoying health lifestyles, but got shut down thoroughly as well.
Even though dogs eat things other than meat, the animal biology expert gave a thorough schooling on why carnivorous diets are so important for dogs - all backed by evidence.
I mean he just keeps on providing more and more evidence and cautions people who want vegan/vegetarian pets to own a gerbil.
Does he come off harsh? Sure, but his anger's coming from a good place: he wants to make sure dogs are being cared for properly, and not as some kind of personal demonstration of how successful their owner's lifestyle is.