The best argument against "net neutrality" legislation was something Jerry Pournelle said on last week's TWiT podcast. To summarize (this is not an exact quote), he asked whether we should trust the Congress to write a law (any law, on either side of this) that would not have some fairly horrid unintended consequences. Never mind the intended consequences.
I know I don't. I'd rather have no new law in this area at all.