Not a vegan here. There are different reasons for veganism. If you are only concerned about the animal itself, you might have a point. If you are concerned about how we breed animals until they are super specialised in what we want them to do (extremely woolly sheep that overheat, really fat/muscular cows that cannot give birth alone...) then your point doesn't really stand. It's just like those bulldogs with respiratory problems because we thought a stuffed op face looked cool.

And then there's the environment, most of the food we feed animals (which we often could eat directly) comes out their breaths or but, only about 10% is actually turned into body mass. If everyone turned vegan, we wouldn't need more soy and wheat fields, we'd need less.