I think that you have missed the point. I don't believe that the intention of the discussion was to size-off the merits of Open Source and Free Software. Rather, my reading of the message was that it proposed that different projects work together to offer greater protection against security threats.
The proposal's intent was clear. I responded it by saying the FSF is possibly interested, and pointing out one aspect that needs to be changed so that the FSF can participate. The message addressed me and other FSF activists under the label of "open source", which is actually the name of a movement we disagree with. We can participate in cooperation on security, but we cannot participate in calling ourselves "open source". To make FSF participation possible requires some simple and easy changes in the way we will talk about what we're doing. It has to be called "free software", so the FSF is not mislabeled. If people who identify themselves as open source advocates are participating also, it should be called "free software and open source", so that they are not mislabeled either. This should be easy to do. I hope that any others who are interested will agree to this change, and we can move on to see whether there is useful work to be done together on security.