Yeah no, that's like saying common sense is the best defense against getting sick. Sure, you know what to do to avoid most common disease and such, but you're also relying on the people around you not having them either, since if any of them do you get screwed over.
Best defense is common sense and having an actual defense for crap common sense won't stop.
just live in a bubble and disconnect from the internet. NO VIRUSES!
But seriously, I use MSE for my computers and never get infected. I have avast, spybot, malwarebyes all with automatic scans and updates enabled for my parents pc and it's still infested with toolbars and fake virus software whenever I come visit.
As my mom always said, there's no substitute for education.