I had a G3 tower for many years and ran OS 8.0, 8.5, 9.0 and the very first version of OS X. I never caught, nor did I ever hear about a single virus. I would like to know where you get your information from.
Also, lets just say you ARE correct. Mac OS X has one single proof of concept "virus" and this recent "trojan".
I still have yet to see anything remotely within even 5% of the malware, spyware, viruses, worms, and trojans available for windows.
So, please, cite...