There seems to be a perfectly reasonable consensus that the ethical argument for free software is not very effective as the prime mover of advocacy toward institutions. That is, getting up in front of your school board or IT staff, explaining that you should stop using Windows or Mac OS X because it is morally wrong to do so, and sitting back down is probably not going to work. This is an empirically observable fact. So free software advocates are told to tone it down, at least until we get our foot in the door, and that's probably good advice.
What is annoying, however, is that people who have made it their vocation to talk to educators about the ethical dimensions of the information ecosystem also don't talk about the ethical argument for free software, even when it is quite relevant to the discussion at hand. Since such people are presumably not doing advocacy one way or another, they shouldn't have to worry about whether or not the argument is literally persuasive in the short term, just whether or not it is important to the conversation, and one would be hard-pressed to deny that free software has not been a (if not the) key innovation in the field of "information ethics" in the past few decades.