I find people who agree with me for the wrong reasons to be more problematic than people who simply disagree with me. After writing a lot about why free software is important, I needed to clarify that there are good and bad reasons for supporting it.
You can audit the security of proprietary software quite thoroughly; source code isn’t a necessary or sufficient precondition for a particular software implementation to be considered secure.
The article focused on studying the behavior and properties of software. For completeness, it mentioned how patching can be crowdsourced with the example of Calibre. I also described how FLOSS decreases dependence on a vendor, and wrote two prior posts about this linked at the top.
I never claimed that source code is useless, only that we shouldn’t assume the worst if it isn’t provided.