That is a crappy argument and actually harmful to Open Source. That applications like Abiword or Gnumeric are free of charge, was a choice of the developers, not a demand of the users. This choice by no means gives those developers some special status or absolves them from justified nagging from users (yes, I'm perfectly aware that I'm nagging; there's nothing else I can do).
Point is: both Abiword and Gnumeric were released very shortly after the release of the Nokia 770 and now, after the release of ITOS 2006, they seem to have disappeared without any explanation or excuse. This is not very nice behaviour towards users, and users of open software are by no means different from users of closed software.
What your remark does, is basically make people think twice about adopting open software. You see, I don't choose open source because it doesn't cost me money, and if open source implies -- as you state -- that I shut up and be quietly grateful for whatever I get, then I'd rather pay someone money to get what I want, whatever the state of the sources.