That comparison seems weird because the relationships aren't the same. Comcast's customers are the people who pay for Comcast service at their homes and businesses. If Comcast favors its own content over other content, and they have a local monopoly on internet service, then they are using their monopoly to abuse their customers.

Neither Microsoft, nor owners of Windows Phone handsets, are customers of YouTube. The only people who are customers of YouTube are people who pay to have their videos hosted there.

Is YouTube purporting to provide me with Internet access or otherwise operate as infrastructure? I must have missed that.

If Comcast wants to provide a digital network that provides connectivity between selected entities (such as end-users and companies that have elected to pay Comcast additional fees), that's fine. But they don't get to call it "Internet". They don't get to pass it off as something different from the AOL and CompuServe of old.

Comcast and many cable ISPs have a monopoly for high speed Internet in many parts if the US. YouTube is not forced on anyone due to where they live, and there are plenty of alternatives to YouTube out there that you are free to use.