I'm a bit of a protective mom. I believe that one can correct a child without yelling at them. Some people believe the best way to get them to listen is to scare them into submission. I have worked in a private school before and you'd be surprised at how "some" teachers will speak to the children. These same teachers are sweet as ever when the parents walk in the door. If she tagged your daughter and not the others, it makes me wonder if she gets annoyed about other things with her (like a personality conflict).
Although I do agree that children need to learn respect and to follow the rules, they should still be treated like a human being and not spoken to as if they're pesky, little, inconsiderate kids (and this is the tone of voice I used to hear at the preschool by some teachers). I don't have a problem using someone else's behavior as a life lesson for my child, but I'd refuse to submit my child to their behavior for a full day, every day. I had to deal with this when my oldest was in 3rd grade. Her teacher was awful (not to my daughter, but she witnessed the teacher's behavior) and my daughter cried every day about going to school. The counselor said something like "she'll run into unfriendly people in the world and needs to learn how to handle it." My response was that she is ONLY 8 years old and that she doesn't need to be subjected to unfriendliness throughout most of her day.
I also understand that some teachers may be dealing with parents that do nothing about their children's behaviors, but it is absolutely wrong for a teacher to just assume the parent wouldn't deal with it and take it upon herself in such a forceful way. I just cannot stand to listen to people talk to kids in a tone of voice that treats them like they're not any good.
Like I said, I'm a bit of a protective mommy. I, most likely, would not stand for it.