Ugh. The old
security through obscurity argument. It's utter BS. I can count on one hand the number of pre-OSX mac that didn't have malware/virus that came in for repairs in the 90's. Zero. Every single machine brought in for repair had some sort of virus...every single one. Apple's market share back then was less than 5%, yet 100% of the machines I repaired had a virus on it. We used to have a betting pool on the number of viruses we would find. I would usually choose 3.
I can count on one hand the number of OSX macs that had malware/virus that came in for service. One. It was ad-ware caused by
PICNIC/PEBMAC.
Pre-OSX mac shares 5%, OSX mac shares 15%. Mac gained market ground with the release of OSX, yet dramatically reduced the amount of malware at the same time. Security through better security, not security through obscurity.