(1) I support network neutrality, but it's a vague term and I support it according to my own understanding of the technical and social issues. I believe that Network Neutrality(tm) as less knowledgeable people have allowed big content providers to define it is broken, and do not support it.
(2) It's not economically feasible to build a network where everyone has guaranteed bandwidth all the time. We don't build roads that way for the same reason. You don't get your own reserved lane, because the whole system is built around the concept of people not consuming peak resources at the same time. Ditto for the electrical grid, water/sewer systems, etc. The alternative would be hugely wasteful, so this is - quite rightly - how our world works.
(3) In such shared systems, occasional or even frequent contention for resources is inevitable. Look at cars and traffic jams again. Anybody who has run a large shared computer system knows the importance of dealing with CPU hogs, memory hogs, disk-space hogs ... and network hogs.
(4) To resolve contention, network operators must make decisions about which packets to drop. They have a right and even a duty to make these decisions in a way that best protects their other users. Utilitarian "greatest good for the greatest number" should be the goal.
(5) Some users and some applications (protocols) respond well to dropped packets or other indicators of contention, by reducing or redirecting packet flows. Other users and other protocols (e.g. BitTorrent) respond poorly by increasing load, crowding out other users even more. Worse, they bring the whole system closer to "congestion collapse" which is when the system is too busy handing reconnection and retransmission requests to do useful work.
(6) "Make no choice" (i.e. drop packets randomly) is really a choice, and one of the worst. It actively incentivizes poorly behaved users and protocols to hog even more of the contended resources, making the network less efficient for everyone (even including the hogs themselves).
(7) Unfortunately, "make no choice" is the only choice allowed by many Network Neutrality(tm) advocates. Whether it's by design or the result of sloppy wording in the resulting regulations doesn't even matter. The consequences are there nonetheless.
(8) Real network neutrality would preclude outright bans of certain endpoints or protocols. It would also preclude throttling of specific traffic when sufficient resources are available, but allow intelligent most-effective throttling when needed. Under contention, this means throttling the most ill-behaved users the most to restore proportionality among all users' service. Traffic jams again. When traffic is heavy, everyone crawls along at the same slow rate.
(9) Real network neutrality would not bind network operators to the will of the big content providers. If a network provider's duty to provide fair service to all of its users precludes a content provider (e.g. Netflix) shoving all the traffic they want through an already-congested part of the system, it's the content provider's responsibility to find and fund other solutions that work with the network instead of against it. Using the rhetoric of "neutrality" and abusing the regulatory apparatus to force a very non-neutral outcome is despicable.
(10) Other kinds of discriminatory or anti-competitive behavior by network providers are already addressed by other areas of law. In particular, anti-trust law should already preclude network providers from getting into the content business themselves, or favoring certain content partners, partly because those would make it impossible to follow the principles outlined above. Content providers (e.g. Google) should likewise be precluded from entering the network-provider space for the same reasons. What's good for the goose is good for the gander. It doesn't get more neutral than that.