So now the difference between a virus and a trojan are important ;) gotcha...
Fortunately, I like chutzpah. :)
Here, let me help you out a little.
Viruses self-replicate. Trojans don't. That's the only difference. But hey, don't take my word for it; see what Symantec and McAfee have to say on the matter.
There is nothing in that definition that has anything to do with route of entry. A virus is still a virus if it gains access to your system by tricking you into executing an infected payload.
In fact, that's how the vast majority of viruses work. Even things that Symantec and McAfee explicitly label a "virus", such as the infamous Melissa worm, work by having the user open a file and invoke a macro.
So if you're going to tell me that a virus isn't a virus unless it uses a remote exploit, I'm afraid I'll take the word of Peter Norton and the U.S. court system over yours.
(Let's recap, shall we? I pointed out that desktop Linux is just as vulnerable to viruses as Windows for all the same reasons. You declared that we should simply ignore the field's single most common infection vector because it doesn't match your personal definition of a virus; however, the industry leaders in virus protection disagree. Your argument is semantic; my argument is Symantec. Then, thinking you were on sure footing among the much smaller subset of infection vectors that do matter within your definition, you went on to express shocking naivete about the robustness of *nix systems against said vector, to which I easily provided a litany of counterexamples that you could've easily found yourself if you weren't blinded by unfounded faith. Is anyone keeping score?)
They sure as heck count to the user!
You and MichiganMan both cite the example of tricking a grandma out of her ATM PIN, and saying that doesn't make the bank no safer than a piggybank (or her purse). Well, actually, the bank is in fact no safer than a piggybank for the grandma.
How easy is it to get the grandma's money if it's in the piggybank? Very easy. How easy is it to get her money if it's in the bank? Likewise, very easy.
Neither money storage mechanism poses much of an impediment to a would-be thief to get the grandma's money, because the grandma herself remains the common point of greatest vulnerability. The probability of a thief getting her money does not noticeably decrease as a result of her moving her money to a bank.
The grandma would increase the security of her savings by making it more difficult for her herself to access them, thus reducing the extent to which a thief could leverage her to get her money. This would include refusing to have an ATM card, or storing her money with a trusted broker. However, it makes it much less convenient for her to access her funds, and it makes her less likely to even bother having a bank (or money, for that matter) in the first place. Most grandmas would not find this a suitable security solution, or even a "solution" at all.
She could also educate herself a little more about scams and other thievery techniques, and take proactive steps to keep her knowledge current and her assets protected. Once again, this is not a suitable solution for most grandmas. It takes away from time that she would rather spend with her grandchildren, and it intimidates her to be burdened with the full responsibility of overseeing the security of her assets.
So as long as the grandma expects convenience, and as long as she remains naive, her assets remain vulnerable.
And if you want her to use your bank instead of the competitor's, and you claim that she can retain both her convenience and her naivete, then you cannot in good conscience do so by claiming that your bank is more secure. It doesn't matter to her how thick your vault door is or how many security guards you have on staff. That's not how thieves will steal from her; your vault door and your guards are about as useful as installing airbags on all the teller windows. They'll steal from her by going through her, and your bank does nothing to impede such an attack.
And if you do manage to convince her that your bank is more secure, all you're doing is exploiting her naivete.
Fun Fact: Did you know you don't have to keep moving goalposts or redefining terms when thoroughly pwned online? It's true! You can accept defeat with honor. People believe untrue or incorrect things sometimes, and, hey, that's okay! When shown the error of your ways, nobody will think less of you for it. A simple, "Well played, sir!", or even quiet concession, is better than devolving the discussion into a game of gotchya's in a misguided and ineffectual attempt at saving face.
Of course, if you want, you can shoot for the moon and try to lose in the most spectacular and unintentionally self-effacing way possible. Typically this involves some kind of application of Godwin's Law. In this particular case, this might involve something like, "Oh yeah? Well, you know who else considered the best route of desktop datasystem intrusion to be through socially engineered exploitation of a largely naive but highly empowered userbase? Hitler, that's who!" I leave the specific implementation to your own imagination.