P2P is already throttled, because of the crippled upload speed that most ISPs implement. Upload is often only 1/10 of download speed on residential internet connections.

I think Net Neutrality should also address this.

Upload speeds are often that low to increase download speeds. If you have the option between 30/30mbit or 50/10mbit, most users will have a much better experience with 50/10. Upload speeds beyond 10mbit/s are rarely noticeable for standard applications of most users (streaming, surfing).

It also kind of prevents people from running servers at home but renting a server with average connection quality (what you'd get at home, no multiple redundancy and excellent peering) is not much cheaper than the energy costs of running it at home (at least in Europe). So I doubt that this is the main motivation for ISPs.

You don't get your point, throttling a p2p browser is neither an example of whitelisting or blacklisting, you can't infer that from a single example. For me it sounds more like blacklisting

If white-listing is employed, everyone not on the white-list is throttled. As peer-to-peer distributed applications typically connect with other users of the application they need only not be included in the white-list to stifle the performance of p2p applications.

ISPs could easily provide you a high speed to Netflix, Amazon, and Youtube's IP ranges. and limit it to 10kbps otherwise.

Blacklisting is complicated because the web is large. The blacklist would quickly approach gigantic sizes and slow down internet while the ISP is scanning requests.

On the other hand, a whitelist can be much shorter (Facebook, Youtube, Google, that's maybe 50 entries including the CDNs) and simpler (don't pay? not in it.)

So, the whole web would be super-slow, besides YouTube and a handful of others?

Wouldn't they reduce YouTube resolutions and similar things, like they've done in the past?

This is fundamentally the same thing.