[cybernautique]

No, a non-employee contributing to open-source software doesn't make them unethical; again, I don't care to lay blame at the feet of a tool.

I take it as axiomatic that Facebook is an unethical actor. I believe I have good reasons for this. From there, I say that anyone who works to make Facebook more effective at its unethical goals is similarly unethical.

No, this doesn't include people that contribute to OSS that originated at Facebook. Improving OSS is a contribution to the community, of which Facebook is unfortunately permitted to benefit from. Facebook starting an OSS project does not make the OSS unethical, because the OSS is a tool.

The question is different for employees because of this community/Facebook divide. Facebook employees are not unethical because of the tools they use for Facebook, they are unethical for furthering Facebook's unethical aims.