I think that's a fine reason for a person deciding to personally not use proprietary software. I think it's a terrible reason to say everyone should only use free software. I'm a software developer, but I don't want to be told "add it in yourself" when I go looking for a new feature, most especially when that feature is already available elsewhere. Certainly, non-programmers do not want to get that answer either! It is unreasonable to expect that of the general population.
To give a concrete example, I choose to use iTunes and/or Windows Media Player because they are easy to use and provide all the features I need without any tweaking; I have never found this to be the case for any FOSS media player. (Quite the opposite.) Why should I spend my time fixing the deficiencies in one of a dozen FOSS media players when I can just use a proprietary one that I know works? "It helps everyone else" is a good ideal, but it is not a good argument. I have better things to do with my time than fix deficiencies in FOSS media players.
My problem with Stallman isn't that he doesn't want to use proprietary software, or even that he thinks proprietary software is inherently evil; my problem is that his reason for opposing cell phones is simply paranoia. Yes, there's a chance someone will use your cell phone to track where you are.The ability to track your location is inherent in the nature of the device - you have to be connected wireless to a tower, therefore you can be tracked with some degree of precision. Has Stallman suggested an alternative technology that allows mobile communication but prevents the device from being tracked? Is it his opinion that we should not use mobile communication devices at all, merely because they can be tracked?
More importantly, why is this small chance that someone will bother tracking my location so bad? It's not hard to find my home address; it's equally trivial to find the address of the building I work in. I must travel between the two locations, so my usual approximate location during commuting hours is obvious. Anyone passingly familiar with me knows I go to church on Sundays, and church building locations and meeting times are also public knowledge. That's all without ever tracking me through my cell phone. I don't care if people know any of that, so why should Stallman's problem with cell phones concern me? I'm not asking why I should care about privacy; I'm generally opposed to government policies that reduce privacy. I'm asking, why I should care that my phone reveals my location when my location is virtually always known anyway?
A good solution to the problem "I don't want to be tracked when I go to location X" that does not require giving up the benefits of having a mobile communication device is to not carry your device when you go to location X. It's a silly reason to abandon mobile communication technology entirely.
As for microphones theoretically recording me, I see no real reason for concern there, either. There is a very large difference between theoretical threats and likely threats. My computer could be recording me, too, in theory, whether or not I'm running open source software, but that theory does not mean I should abandon the use of computers, nor does it mean that computers are "tools of Big Brother".
I'll say this another way, because Stallman and many of my fellow Slashdotters apparently don't understand the concept: in any society, we must give up some degree of privacy in order to interact with one another. It is stupid to make interaction with each other much harder on the slim chance that someone might use a person's cell phone to track or listen to that person.
Yes, there's always the possibility that companies will screw up their software, or remove features, etc., like Sony with OtherOS. "Only use FOSS" is not the only solution, nor is it even the best solution in many cases. The most practical solution is to not buy from companies that do this. Companies aren't stupid; if they know removing features will result in a tangible loss of sales, they won't do it. (The problem with Sony right now is that they don't see a tangible loss of sales; we have nobody to blame but ourselves. I am seriously flabbergasted when people's solution to "Sony sucks, they took away OtherOS" is to buy a second PS3.)
I'm not opposed to Stallman having his own opinions, but he's really taking this to an absurd extreme. Supposing the hardware were "open source", that doesn't help; it's much harder to fix a hardware bug than a software bug, even if you have the schematics and the expertise. Other people can't get your fix merely by grabbing your changes from source control, and without expensive equipment and/or disassembling your device piece by piece, you can't even verify that the device you're holding matches the schematics. Open source hardware is only useful to a point.
As for Stallman's reference to Stalin.... I'm pretty sure there's a name for the logical fallacy where you invoke people's emotions to make your point, rather than actually making logical arguments. Let's look at what he said:
"It's Stalin's dream. Cell phones are tools of Big Brother. I'm not going to carry a tracking device that records where I go all the time, and I'm not going to carry a surveillance device that can be turned on to eavesdrop."
Yet he offers no evidence that cell phones are tracking devices which record where we go all the time (i.e. having a GPS does not automatically mean the device is recording our movements, let alone reporting those movements to anyone), nor that they are being used as remote surveillance devices. His only argument is the emotional one, playing on people's fear of Stalin's brand of communism, and the speculation (implied as fact) that the government will track your every move and listen to every sound you make just through your cell phone... merely because you have a cell phone. His argument is made even more stupid by stating that mobile devices running Android are just as untrustworthy as the rest merely because carriers include proprietary software on them, ignoring the fact that tracking is possible regardless of what software is on the device, as long as it is turned on, and ignoring the fact that you can simply remove the proprietary software.
In other words, the only basis for his argument that we should not use cell phones is pure and simple paranoia, and that, my fellow Slashdotters, is why I don't care one bit what Stallman says about cell phones (or really anything else).