The biggest opposition is that it was completely legislated without teacher input, and without a clear plan of how any of it would work and whether it would be funded 3 years from now. I'm a teacher who is opposed to it on those grounds, but not entirely opposed to all of the ideas. It just reeked of dirty business (like the way the online classes have to be done).
On a side note: student motivation has always been one of the biggest hurdles for any educational system. If students can be motivated to take online classes, they very well may work, but that's been one of the biggest advantages of in-class lessons, is that the learning time is set aside, and there is someone there to help clarify concepts.