That's technically not a Net Neutrality argument, which is why the argument existed in the first place. To some extent, Comcast was right: it wasn't funneling as much data to Level 3 as Level 3 was funneling to it. What Comcast left out was that this problem was 100% of its own making, and impossible for Level 3 address: Comcast only sells highly asymmetric pipes to highly asymmetric users. It is actually illegal for its users to try to create a situation where it will funnel as much data to Level 3 as Level 3 funnels to it. Which is why techies were incensed by the argument.
That's the issue. All techies know the huge holes that have to exist in NN for the Internet to work. No one disagrees with any of those. The problem is that the principle of NN is all we have to concisely explain to people why Comcast is being an utter monopoly-rent-seeking shithead in this discussion, and how Comcast's attitude will break the Internet. Anything more requires delving into the depth of QoS, CDNs, dark fiber, roll-out subsidies, last-mile topologies, and barriers-to-entry in the website market to make a coherent argument. No one in the public sphere is going to listen to that.
That's why NN keeps being brought up. It's the only sound bite that's remotely applicable, and unfortunately, sound bites is what wins political wars.