So this is something of a multi-part response, corrections appreciated. Full disclosure I am highly pro-Net Neutrality, although I believe the authority problem is complex enough that congress should just pass a bill mandating it, to clarify the situation and make it harder to undo.

0. In the US, there's a legal status for telecom companies called "common carrier", and multiple subcategories (Title I, Title II). Basically common carrier status says that you have to abide by certain regulations around who you serve, and in return your company gains some benefits (among them, they're not liable for illegal material transmitted over their networks). So your phone company, a Title 1 common carrier, can't charge you more to call Best Buy than to call Amazon, but if you plan out a bank heist with your buddies over the phone, the phone company CEO doesn't go to jail. Right now ISP's are classified as the less regulated subcategory, Title II.

1. The first question, orthogonal but critical, is whether the FCC has the legal authority to set and enforce policies around net neutrality to anyone at all, or only Title I common carriers. The exact authority to do this was never enumerated to the FCC by congress (because the FCC was set up long before the internet). There's also a question of whether the FCC can just reclassify ISPs as common carriers at will. There is an ongoing legal dispute that the FCC has currently lost at the DC Circuit court level where the court said that the FCC can't regulate net neutrality without reclassifying ISPs as the more regulated category. The FCC then reclassified them, which is in the courts. I bring this up because it's one argument given by republicans who oppose it: They don't believe the FCC has the authority in the first place, some believing it's the FTC's job, some believing that nobody has that authority until congress gives it out. Those who feel this way generally don't think congress should give that out. The most used reasoning i've read is "Things have been fine for 25 years, why add more rules now?".

2. Assuming you think the FCC has the authority here, net neutrality as it's been laid out since 2010 basically says "all lawful bits are equal, with reasonable allowance for quality of service". You can still charge differently for different amounts of bandwidth, but are not allowed to block or modify traffic by type or source. Wiki has a nice summary here: [1]. Peering agreements between bandwidth providers are also still legal. The quality of service stuff is beyond my level of knowledge, but I believe it's intended to allow for things like blocking denial of service attacks or taking links down for maintenance.

Without it, ISPs are free to discriminate based on source, content type, etc. So they can charge you more for just video services, or slow down just netflix but prioritize hulu, etc. The nightmare scenario for many internet advocates is that image you've probably seen of an ISP ad with different packages for allowing gaming, video, etc. [2]. For the record, comcast has promised not to do this.

Another worry of open internet advocates is that the ISPs will go to Netflix, Amazon, etc, and ask them to pay more to guarantee quality of service. This could raise prices for these services. If this included speedups over competitors, rather than just slowdowns of big bandwidth users, it would discourage competition from startups who couldn't pay huge amounts like major companies.

The counter-arguments vary, but tend to fall in a few camps:

a. ISPs have not done this in the past, so why add more regulations and increase their costs of doing business (more legal costs to understand the laws and ensure compliance).

b. Market competition will ensure that if one company starts ripping off consumers, another will move in. Regulation is unnecessary and may have nasty second-order effects.

c. If Netflix is taking up a non-trivial percent of Comcast's total resources, why shouldn't they have to pay more? Same for game networks, etc. This is especially interesting with file-sharing services, which are a big bandwidth suck are commonly viewed as mostly illegal activity (piracy).

d. These companies are afraid to start new lines of business that will employ people and help consumers. I've yet to dig up any good proposed examples, of anyone at HN knows of one that would be cool. Pai in particular has mentioned this a number of times.

[1] https://en.wikipedia.org/wiki/Net_neutrality_in_the_United_S...

[2] http://www.theharlemvalleynews.net/wp-content/uploads/2017/1...