I don't know if they could prevent him from owning any site that has the name Kindle in it. Surely he could register
www.kindlesucks.com if he wanted to and claim freedom of speech. There is no way that website would be assumed to be endorsed by Amazon.
Or maybe he could do like
BlogKindle.com and stick an "Unofficial" label in the banner of his website.
Personally I like the Kindle and Amazon's pricing of ebooks, when that damned "Agency Model" isn't involved. But I prefer the touchscreen on my new Sony and its support for the epub format.
Etienne66