Apples and Oranges
The Mac can even run Windows—so it’s compatible with the PC world.** With one exception: It doesn’t get PC viruses.
Pure marketing talk hiding the following facts:
1) There are antivirus products for Macs and they do have a use
2) Running Windows on the Mac (either in a VM or using BootCamp to boot directly into Windows) means that you can get PC viruses (on your Windows OS) and as a result they could damage your files or do network communication to send out your personal data etc. (spyware).
So you could eventually get the (best) viruses of both worlds 🙂 if you believe the marketing hype and don’t follow good administration/usage and web navigation practices with your MacBook Pro.
For Windows you could install the free AVAST Home Edition antivirus for example and also use Microsoft’s free OneCare virus scanner from Internet Explorer now and then (and maybe also Trend Micro’s free HouseCall scanner and Kaspersky’s free online virus scanner). Plus if you find a suspicious file upload it to jotti’s multiple antivirus scanning service to see what various antivirus engines say about the file.