You say, "Where there have been a handful of questionable actions in the past on the part of a few companies, the Commission and the marketplace have responded swiftly. The case has simply not been made for what amounts to a significant regulatory intervention into a vibrant marketplace." Essentially, you are claiming that since no carrier has been bold enough to actually implement a tiered structure, they won't.
You must realize that in many cases we're talking about the same companies that charge more to send a single SMS text message than it costs to retrieve the same amount of data from the Hubble telescope. The terms "fair" and "reasonable" aren't in these companies' dictionaries.
If Net neutrality is tossed out the window, the next Facebook or the next Twitter will not even get off the ground. Instead of a small company with a great idea and a groundswell of users and contributors, those with tiered Internet will be blocked from accessing a budding business Web site, perhaps with an interceptor page offering to give them access for only an additional $5 a month. On the other end, the carriers will have their hands out to a fledgling company for payola to add the company's Web site to their tiers. Naturally, this is in addition to whatever costs the site already incurs for raw access. If you want to discuss stifling of innovation, there you have it.
The fact is, Senator, that if your amendment comes to pass, explicitly prohibiting government involvement in maintaining a neutral Net, they will do exactly that absolutely as quickly as they can. You will be serving them an exquisite meal made from the technological and innovative future of the United States.