GNU/Linux Is Very Secure?

Bana, a fellow DocIslander, told me about an IBM DeveloperWorks titled Anatomy of Security-Enhanced Linux (SELinux). Bana pointed me to the following excerpt:

GNU/Linux is very secure, but it's also very dynamic: changes can appear that open holes into the operating system that can then be exploited. Although considerable attention is paid to preventing unauthorized access, what happens after an entry has occurred?

Good! Oh, hang on a sec. Don't you smell something really fishy in the first sentence? Let me me help you out a bit:

GNU/Linux is very secure, but it's also very dynamic...

I let my mind chew on these memes and I came to the conclusion that this basically boils down to saying something similar to the following:

Have no fear chap, you can sleep assured that no burglar will enter your house. Look at the door. It's made of bulletproof metal, 6 inch thick with 17 different locks, retina scan and ADN sampler. Oh, by the way, it's a very dynamic design that's why we are destroying the surrounding walls and rebuilding them from the ground up.

... And that's why we need something as mind-bogglingly complex as SELinux to secure the very secure.