I know what you're saying, but I've always had a problem with that as an excuse.
The OS is supposed to protect from problems with the app. When Windows95 was constantly brought to a screeching halt by a problem with an application, folk never said, 'The operating system is fine, fix the app.' Instead, MS was forced to build better memory protection into their consumer operating system.
As far as I can see, the same situation applies here. The OS should not allow exploits built into applications to render the user's machine open to attack. Hard I know, but that's the way I see it.
Furthermore, Apple makes a big deal out of how much better it is to build the whole widget from the ground up, so I'm a little surprised when Safari (Apple software) blows a hole in OSX (Apple operating system), rendering the Mac (Apple hardware) open to attack.
As I said, that's just the way I see it.