Re: iOS PCs?
Some actual facts for you:
1. The issue here has nothing to do with the various definitions of malicious code, and what category they fall into. It's the fact the Mac made the claim that such an attack could never happen, and it has. Aside from that, the definition Trojan has nothing to do with its delivery method. It could be deployed by a virus (self replicating malicious code), a worm (similar to a viral infection that spreads within a network infrastructure), a piece of malware, spyware or whatever. All the Trojan definition specifies is that it will give access, control, or information from your computer to someone else. Some people might even label remote administrative programs such as dameware, vnc, or logmein as a Trojan.
2. In 12 years apparently a lot of Mac users like to play word definitions games between what constitutes as a Virus. As you said, there have been Trojans in the past.
3. I'm not susceptible to the thousands of virus's that plague plant life, yet you don't hear me going around saying how I'm impervious to all infections. This is very similar to making the claim that a Mac can't get a Window's virus. Apples and Oranges as far as the code is concerned.
The lack of Virus's for mac's has very little to do with how secure or insecure the OS is, and has quite a bit to do with the lack of available targets compared to other alternative operating systems.
4. Your statement right here doesn't even make sense. Maybe you could try again to explain how a "Mac keeps you safe from unknowingly downloading malicious software" if it can't prevent you from "unknowingly downloading malicious software”?
Also, your claim that it’s impossible for a company to develop this kind of protection is false. It's called a virus scanner.