When I was young many, maybe most, of the electric utilities in the USA did all the functions. They generated the power, sent it onto the grid they owned & maintained, it went onto the last mile wires they owned & maintained and they exclusively sold it to end users.
Comcast could have emulated that situation under the previous lack of rules or laws. They create & distribute content (NBC, Golf channel, Weather channel, SyFy, Universal Studios, etc.), they own enough nationwide backbone distribution for their needs, they own and exclusively use last mile connections and they exclusively sell to end users on the last mile. To close the last loophole all they needed to do was block content that wasn't their own and they had an old electric utility style end to end monopoly.
So to me it's easy to see why people would make the analogy and why people feel NN, which now blocks Comcast from implementing that final step, is helping.
Myself I haven't looked at it this particular way because I'm not a Comcast customer, I have Charter Cable. However that is likely to change very soon, part of the Time-Warner & Comcast intended merger includes swapping a bunch of customers with Charter. This is meant to please the FTC & SEC, Charter ends up with a net increase and Comcast/Time Warner ends up with a net reduction in last mile customers. This happens while making both companies more profitable by consolidating their customers by region. Comcast will own all cable service in the entire State of Massachusetts.