Your original point seemed to be that FreeBSD is more secure than Linux. I'd say you haven't made your point.
He doesn't really need to.
I contend that if you are making an argument then it's up to you to support it. Clearly, he doesn't need to convince you. That's well and good but it still leaves the point as conjecture.
In the CS community, it's well known that BSD is more stable, secure, and the best OS for critical infrastructure, while Linux is more friendly, flexible, and better for hobbyists or businesses that can save money (by hiring cheaper Linux fanboi rather than expensive real computer scientists).
I always find it interesting that people want to refer to the outcome of applying a complex and nuanced term like "security" to some product as being "well known". Speaking as a member of the aforementioned "CS community" (a la Dijkstra :-) )