Cows don't just produce milk because they are magic. They have to become pregnant first, and then over and over again.
I'm not vegan. But from what I am aware, vegans primarily don't drink milk because of the whole veal thing.
If a cow had a choice, I doubt it would choose yes. I'm sure they love their offspring as much as most/all animals do.

If they said it was OK... I guess it would be OK. But that would seem kind of sociopathic wouldn't it?

Another thought. It's illegal to eat a person, even if they say it's OK. But is it ETHICALLY wrong?