At any point along that line, Comcast can throttle Netflix, and you are still stuck with taking the data at the pace they decide to deliver it.

Yeah but no. The FCC regulates the arrangement the end user has with Comcast. They decided that the Internet wasn't a utility. But as soon as Comcast decides that they get to interfere with a potential competitor (which is what you are, as a Tier 2 peer), they walk smack dab into anti-trust.

If you don't have any choice but to work with Comcast because of an arrangement Comcast has as a Tier 1 provider, and Comcast doesn't allow you to use that Tier 1 network as a peer, the FTC comes down like a shithammer on Comcast. It's no longer an FCC issue, it's garden variety anti-trust and Comcast wants to not set that precedent so hard that there's no reason they'd ever do it.

The telecoms know the future. They know their time in the sun draws to a close. They're making money while the sun shines and transitioning to content (there's a reason it's Comcast Universal). The whole Net Neutrality thing is a staying action, not a victory and they know it and the longer they can keep the government from making them behave like a utility the more money they make.

But they can't keep doing it forever. And a precedent like fucking with a peering agreement would end the party faster than just about anything else they might try.