Ok, show me one win7 malware that installs as soon as I plug it on the network. I will even take my windows 7 machine and browse to whatever site you like me to go to and see if I get infected.
Time to put up or shut up.
Ah, suddenly you're narrowing the issue to a particular version under very limited conditions - conveniently avoiding the host of other malware vectors and the long history of the issue and the many version still in use and the new vectors which keep popping up. Sure, the absolute latest system with all the latest anti-malware patches in place is pretty robust because all known attack vectors are covered ... but that requires considerable time, effort, knowledge, and software to keep that level of defense up. Thing is, if you don't keep expending that effort & cost, won't be long before you're vulnerable to the next "zero-day attack", some of which will be drive-by infections.
How about we first start the challenge with a Mac, out-of-the-box with no updates or extraneous anti-malware programs installed. You can plug it in and load software and visit sites however you like. Only caveat is you don't enter the administrator password without knowing it's for a legitimate purpose.
While stewing over that, you might want to peruse http://techlogon.com/2012/03/23/how-windows-gets-infected-by-malware/ and its discussion of "drive-by infections". And consider that the point of this thread is that ONE botnet has been discovered on Macs, while botnets on Windows doesn't even make news 'cuz there are so many.
See, the difference is that while maybe you're currently protected against drive-by infections, you'll have to keep escalating the defenses because the core design of Windows is susceptible to such attacks ... while OS X, at core, isn't.
