You can say that about any software. By that logic you could denounce indie games or word processors or to-do list software. Even if it's open source it could have been built with a contaminated compiler that installs backdoors that root your system and report all your network traffic to the Freemasons.
In theory - any of course. But we are talking about the level of the risk here. DRM gives you more reasons to expect it to be malicious. Because it's built on contempt towards you (the user), on treating you as a potential criminal by default.
I've used a lot of software that was obviously designed with contempt towards the user: Lotus Notes, ClearCase, and Xilinx ISE to name a few. Netflix's streaming software is not one of them.
Netflix runs custom clients to make sure I'm authenticated and authorized before streaming video to me and streams it in a format that only their software can decode. Sometimes these clients are built into my TV and other times they are written in Silverlight and are built into my browser, but that doesn't automatically mean they're a rootkit any more than Lotus Notes is a rootkit. The only reason it seems otherwise is that you have this weird manichean worldview where any DRM is morally equivalent to the Sony rootkit.
The view I have is that DRM is always prone to be a malware, because it always treats users as infringers. Sony rootkit just proves the point. Trust should be mutual, otherwise it's not trust. If they treat users as potential criminals by default, users should treat them as potential criminals by default as well.
DRM is unethical not because it's always a rootkit. But because it's overreaching. The fact that it's prone to be malware just demonstrates the potential for abuse of overreaching preemptive policing.
Why not? Untrusted code running on your computer is a clear security risk. And you still didn't explain why DRM should be trusted, when it doesn't trust you.
It's the question of the level of trust. Some code is trusted enough to run it. DRM is never trusted enough to run it (IMHO). You seem to be saying that since there is always risk, one shouldn't care about anything at all.