If students are customers, then the university is a business.
A university is a business, and poor business practices will make it go broke, and some have or are about to. But it is more than that, and professors are more than suppliers of a service. They are also paid authority figures in an environment where the "customer" is suspicious and resentful of authority (an authority that makes them work, for one thing, but that can also be arbitrary and harmful for another). To make those "customers" the sole arbiters of instructor performance is to provide disincentives for that authority to demand student performance. That isn't what we're after.
There are, for most universities (the one at which I work, for example - I'm staff, not faculty, so I have no real dog in this fight) existing systems of instructor performance that run from peer evaluation through department chair all the way to the various faculty committees and ultimately to the university president. These can, but rarely do, supersede tenure. Some do take student evaluations into account, especially the written comments pertaining to abilities to communicate and address student questions. The ones at our university are open only until just before finals, and contain the question, "What grade do you anticipate receiving?" which is a rather indirect way of weeding out chronic malcontents. The system is far from perfect but it is, IMHO, far better than taking anonymous student web complaints at face value. Hard-guy professors aren't always bad-guy professors, and students aren't always as interested in learning the material as in getting the grade and proceeding onto the next station in their educational pilgrimage.
However, for public universities there is also another customer, who pays in many cases more than the student customers do, and that is the taxpayer. State boards of education are very rightfully concerned with not wasting that customer's investment, and these are very rightfully subject to the vicissitudes of state politics. Faculties who take that coin know perfectly well where it comes from and sneering at attempts to control it as Republican plots is, IMHO, more than a little disingenuous on the part of the author.
Bottom line: I think the bill is a bad idea but I think the author's objections are a little specious.
+1