There's a bit of a difference between saying you can't stand a teacher or think he or she is bad at teaching (the right to which nobody is trying to take away, so don't try to paint this as FIRST AMMENDMENT RIGHTS!!!) and creating a web site
dedicated to your hate of that person and encouraging others to join in. The word "hatred" + inciting others towards it? I would indeed consider the latter to be bullying; if you don't, then it shows you're pretty out of touch with what bullying is and how it's defined these days. And spare me any whining about that definition when the studies are pretty clear that shit like this is tremendously damaging to the people who are the victims of it.
Now, yes, I'd expect most teachers to be more thick-skinned than most students and not be too bothered by this, but schools have to set a standard and not allow it, period - you can't tailor the punishment to how badly the person is affected.
The school may have a side that shines some light on it but I'll place my money on it not justifying the actions in the least.
The article gives no impression it even went to the other side or even did any real research into the situation. It's reporting just the contents of the lawsuit, which if you know anything about lawsuits, you should realise are going to be a very coloured version of events.
Also,
She was not removed from her AP classes (plural), just the class (singular) taught by the teacher she hated (her words).
From one of the comments in the thread. No source on this, granted, but I'd wager it's the truth.