First, a bit of context.
Richard Stallman, father of the free software movement, has struggled all his life trying to explain that the "free" in "free software" is a "free" as in "freedom", not as "free beer".
Now, let's say someone argues that the main reason for adopting free software is that it has no cost (free beer). How can I tell him that he would make Richard Stallman go mad by saying this?
Is there an idiom that could communicate this effectively? (Obviously, this is a language question, not a free software debate.)
Edit: I just realized that I am looking for a version of "to turn in one's grave" for alive people :)