With all due respect, I think your rebuttal could be summarized as follows:
I'm an open source supporter, and the author has gored my ox. Despite stating quite plainly that open source was no more insecure than 'commercial' software, just not better as some people have claimed, he must be wrong because ... well, just because.
I have an opinion that things are different, though I have no real proof to offer at this time.
I would prefer the author discuss the concept that 'commercial software != open source software', because I think that is more interesting.
I would also request the author consider this poorly fleshed-out example, which does not actually conflict with the article. My intuition is that somehow combining open source and "closed, professional development" would be somehow better than current practices, even though I can offer no reason for such an outcome.
Wouldn't a simple "You're wrong, dead wrong" have sufficed?