Of course it's his choice to be vegetarian and not vegan. But that is so needless to say. It's Jamie Olivers choice to eat meat, too - and Morrissey condemns him for it. "Well, it's my coice" is no jusification for anything, think yourself before a judge, justifying yourself for a crime by saying "but it's my choise".
Anyway, the thing is, apart from all problems in der dairy industry, it is NOT POSSIBLE, to have a dairy industry (and not even a small dairy farm) without killing animals. The argument that eating meat means killing animals, but eating dairy is just harvesting their givings, which has been laid out here, does not carry you very far.
Think about which animal lay eggs and give milk. All of them? No. Only females do. But to do so, they must produce offspring, and the offspring is 50% male. So what happens to the males? Are they taken as pets? Just fed and left on the grass til they die a natural death? No. They get slaughtered. Meat is a NECESSARY byproduct od dairy production. And it takes very little thinking to grasp this, especially when you act as an animal-welfare expert, which M. does. So, yes, it is surprising he manages not to see it.
Now, you can draw two conclusions from the fact that dairy involves animal slaughter: either become vegan. Or, acknowledge the fact that life and death go together, and that the best we can do is strive to have a small sustainable way of farming animals.
Morrissey, however, does neither one. He doesn't go vegan and he keeps condemning people who eat meat, even if they try to do so in a responsible manner. And that IS bewildering for someone who acts so smart and tells everybody off. Isn't it.