I didn't say dual booting was itself the source of the danger (though it is true that in days gone by that was also a source of problems).
The issue I had in mind was the unrestricted hardware access that Windows has if it is running natively. This is an operating system that has literally pushed updates that inadvertently deleted user data, among other severe problems, and that will deploy its updates automatically to many users. Dual booting won't ensure the integrity of your system against that kind of threat. Running Windows in a virtual environment means it can't damage the rest of your system even if it deploys a seriously broken update without warning. And that kind of virtualisation is getting more practical all the time even if for now it remains the preserve of serious Linux hackers.
The issue I had in mind was the unrestricted hardware access that Windows has if it is running natively. This is an operating system that has literally pushed updates that inadvertently deleted user data, among other severe problems, and that will deploy its updates automatically to many users. Dual booting won't ensure the integrity of your system against that kind of threat. Running Windows in a virtual environment means it can't damage the rest of your system even if it deploys a seriously broken update without warning. And that kind of virtualisation is getting more practical all the time even if for now it remains the preserve of serious Linux hackers.