Robert Galbraith / Reuters Netflix CEO Reed Hastings gestures while speaking at the Facebook f8 Developers Conference in San Francisco September 22, 2011.

If you own the highway as well as several of the vehicles that use it, is it fair to tax everyone except your drivers? That’s essentially what Comcast did when it decided to exempt its TV-based Xfinity “On Demand” service for the Xbox 360 from counting against periodic data caps, effectively un-leveling the playing field. Comcast’s defense: The service is delivered over its private IP network, not the public Internet.

Should that exempt Comcast? Absolutely not, according to Netflix CEO Reed Hastings. “Comcast no longer following net neutrality principles,” writes Hastings on his Facebook page. “Comcast should apply caps equally, or not at all.”

(MORE: A Netflix Cable Channel? Right for Netflix, Possibly Right for Us)

Comcast’s private IP network still intersects with the Internet where streaming rivals like Netflix or Hulu are concerned. At some point, any streaming service must, by definition, traverse an ISP’s private IP network to get to consumers.

Hastings says he spent the weekend “enjoying four good internet video apps on my Xbox: Netflix, HBO GO, Xfinity, and Hulu.” But he complains that while Netflix, HBO Go and Hulu count against his Comcast Internet data cap, Comcast’s Xfinity app doesn’t. Hastings continues:

For example, if I watch last night’s SNL episode on my Xbox through the Hulu app, it eats up about one gigabyte of my cap, but if I watch that same episode through the Xfinity Xbox app, it doesn’t use up my cap at all. The same device, the same IP address, the same wifi, the same internet connection, but totally different cap treatment. In what way is this neutral?

A simple enough question with an even simpler answer: It’s not. The question of whether it violates actual net neutrality rules as well as Comcast customers who’ll probably defend the ISP because they’re getting something for nothing notwithstanding, it’s the principle that matters here. You either make the playing field as level as possible, or establish a precedent whereby a highway’s proprietors, with their own vested traffic interests, control who pays at the toll booth and who doesn’t.

MORE: TiVo Gets Comcast’s Xfinity on Demand