In this case, you're right. I don't know that I would make a general rule out of it, though. Maybe in general open source helps, but in this case (for several reasons, including that OpenSSL seems to be a barely understandable mess, or "written by monkeys" as some put it) it didn't.

I agree that thinking "open source magically makes software better and more secure" is absurd. I also agree that Jim Zemlin's statements (in general, in that article) are more of a PR thing than accurate statements.