I could see it being shady if you were talking about denying people access to things they need, but we're talking about selling on the Internet here. It's not like people will have a hard time buying Apple TVs or Chromecasts because they aren't on Amazon. They just have to type the name into their address bar.
I would guess they got a lot of complaints from people who said they couldn't get Instant Video to work on their streaming devices, someone calculated the cost of customer service vs profits of selling those devices, and decided it wasn't worth it... how is that any different form any other retailer choosing to drop a product because it isn't working for them? Customer service costs and returns are probably the most common reason for anyone dropping something.
I know Amazon has a bigger selection than pretty much everyone, but does that give them a moral imperative to not discriminate on products? Seems like people are considering Amazon as if they were a public utility, which seems like a pretty impressive achievement for them.
That's because google and apple aren't the Walmart of the internet, they make electronics. Amazon specializes in selling stuff, google and apple make stuff and also happen to sell them on their website, or you could buy it from somewhere else (in google's case)
I think the equivalent for Google would be deliberately not listing duckduckgo or bing in search results for "duck duck go" or "bing".
But this is literally the first time that I've seen Amazon play that way. So it may not be different from any other retailer, it's different from how Amazon used to be. (Or at least was perceived to be, which amounts to the same thing.)
Now I don't know the licensing terms they have with the content providers, but they certainly aren't fulfilling the consumer demand.
Digital music sold used to have DRM, because it just couldn't be avoided since the licensing terms of the content required it. The Primecast seems likely to be the same.
It's more like them saying, "Sorry, user, we can't let you do that."
Where as this (and what Apple does) is more like, "What's that user? You want <competing thing>? Well, fuck off!"
Thinking on it though, massively slowing down deliveries of books from publishers Amazon doesn't like was actually the first time I've seen Amazon do something like this. So this actually isn't the first time; now its a pattern.
Side rant: Amazon Prime's media crap is also especially annoying to me personally, since I spend most of the year outside of the US, where it doesn't work at all. (Go Netflix!))
(But it's perfectly fine for Amazon's search to only show Amazon stuff, because universal search is not part of their claim.)