The "discrimination" at issue in net neutrality is the same sort that allows you to tell certain people to leave your home. No one has a right to use an ISP's services on any terms except those set by the ISP. The issue is the right of ISPs to make use of their property in a way that benefits them, without inflicting harm on anyone. It is the same right that allows you to tell a Jehovah's Witness to leave your front porch.
Moreover, if ISPs block sites that their customers want to access, their customers will flock to a different ISP. In Boulder I have the choice of at least three high-speed ISPs, plus dial-up providers. The folly of net neutrality boosters is that they have a solid-state view of the world. They are so focused on the notion that ISPs might boost the speed of some sites that they miss the possibility that other ISPs will fill the void and provide fast access to content disfavored by other ISPs.
A vote for net neutrality is a vote against the right of all Americans to use their property as they see fit.
The internet may be a public forum, but access to the internet is controlled through private gateways. For that reason the common road analogy fails, unless you change it slightly.
Net neutrality is not concerned with the roadway; the piece of the internet at issue is the "car" websites drive on the "roadway." The ISP is the website's vehicle for accessing the internet. While the "speed limit" language makes us think of signs on the road, what net neutrality is actually the equivalent of is forcing everyone to drive a Yugo.
What network freedom would allow is for websites, ANY website including coloradopols.com and watchtower.org, to buy the "car" that suits their needs. If my text-only blog works fine at Yugo speed, I don't need to buy a Cadillac - but why should Congress forbid coloradopols.com from buying a better vehicle if they want it? Moreover, why should Congress mandate what kind of cars ISPs sell and who they sell to?
Access to the ISPs' property, just like access to my front porch, is not a right. It is a privilege, bought and paid for by the speaker.