UPS doesn't care if it is a Nike shirt or a Gucci shirt in a box, They just deliver the box where it is meant to go. Why should it be any different for an ISP?
While I like NN there is a strict different between an ISP and UPS because of the digital/physical realm.
When UPS delivers a Nike shirt they have to deliver that specific shirt to that specific person. An ISP needent deliver a specific shirt that originated from Nike Factory to that specific person; they can give a "locally" stored copied of the shirt. This means that the ISP could locally store say the top 4 million songs and so the expense of delivering those songs is practically zero while transporting a song from LA to NYC covers significantly more miles of fiber.
An ISP that wishes to store a "local copy" of t-shirts or songs, in order to make more money, can store a Nike t-shirt just as easily as a Gucci t-shirt, and can store a Nikki Minaj song just as easily as a Gucci Mane song. Thus, nothing actually blocks the ISP from treating the two equally.
Alternatively, the ISP can store nothing, and just be a basic ISP. Nobody is forcing them to store anything, much less do so preferentially depending on brand. And if they personally choose to, to make more money, it's their responsibility to make sure they don't differentiate between brands, because that violates net neutrality.
So, opt-in versus required. Net neutrality certainly allows special pipes and protocols to be set up where desired, if you desire to stretch the analogy beyond its intent.
If you can make a reasonable argument that one kind of data or another creates a meaningful hazard for the pipe that carries it, please do.
UPS does not care what what they're carrying unless it shits or explodes. Anything meeting most of your criteria, they simply will not ship in the first place. Net neutrality specifically mitigates rent-seeking behavior, implying if UPS knew there was something expensive in the box, they'd shake you down for more money to ship it. The only time they do this is in handling hazmat.
They sort of do this in reverse though when it comes to damage claims. They'll first try to find a reason not to pay out, but once they know what's in the box, they angle to reimburse you the least possible amount of money for it. I can't tell you how many times we would lose/destroy priceless stuff like a signed baseball from some World Series and write a check...for the $3 it cost to buy a new baseball (TBF, especially with prototypes/historical artifacts, many such claims are dog-ate-my-homework fraudulent).
Here's an actual case: a container ship carrying designer leather products from Italy took on water and a claim was made for $100k worth of retail losses. We were never going to pay that, since there's no guaranteeing any amount of it would have sold at that price, and anybody that makes money from loss is either profiteering or committing fraud (see: coffin ship). The most we would have paid out was at the price the factory sold it to the designer for ($2-$10 per diem), but IIRC we denied it since no damage was reported along the way. They didn't insure anything, on paper $100k worth of product was lost, and they didn't give a shit-- in reality they lost $2k in drop-shipped crap stamped with an expensive logo. Designer goods are inherently worthless.