Yes, again: https://www.fsf.org/news/fsf-responds-to-microsofts-privacy-... with a completely bogus jail analogy. FSF is on a witch hunt, and I dislike it very much.

Regardless: sharing zero-day exploits ahead of time is way different from actively inserting backdoor code into the OS.

How is it way different? It's exactly analolous to providing a backdoor -- giving means to take advantage of the weaknesses. Whether the vulnerabilities are there by purpose or for by accident doesn't change the fact how exploits are provided and for what purpose.

It would be naive, if not outright dishonest to believe that exchanging 0days is not for offensive purposes, especially after knowing the extent NSA actions go, and of course remembering Stuxnet and Flame.