With caveats, I respectfully disagree with two of your premises.
1. I like to do some dangerous things on this machine. I use Linux. I've had problems. Some of the people I know who do some dangerous things agree that a broader group of mac users have problems because more people write malware for the Mac, however recent MacOses are about as difficult to write malware for as Linux -- which is to say Linux is less safe than people realize. Of course I use clamav. I still do dangerous things so I am responsible for what happens.
2. Linux is not "graphically superior." Linux is a kernel which is packaged with the GNU tools, (usually) X-Windows and various other packages and tools in several distros. Some of these, when run on proper hardware, are graphically superior. Not all. As a satisfied Linux user I am not going to defend Windoze. At all, but at the same time, the chief benefits, even in Graphics, Linux has offered come from, the straightforwardness of configuring hardware when that is permitted by the hardware, and by the range of choices Linux offers.
No I don't just see this as nit-picking. If I wanted to pick nit I would point to the "It requires less demands on system resources". It certainly doesn't require as many system resources but it absolutely demands an awful lot of the system resources it uses. It is a very efficient OS. Period. That's a nit, though. I agree and disagree.
Anyhow, put it in terms I'm completely comfortable with, I shall only say of course everything I did not explicitly disagree with is dead on, and try to phrase this simply.
I'm influenced by the radicals, of course. I don't have to buy the criticisms of Linus Torvalds and Canonical for their avowed willingness to compromise with the proprietary vendors. What the radicals say is "free as in freedom, not free as in beer." That is a really simple concept and it's why it takes a lot of ignorance to suggest Canonical or Red Hat, for Goodness's sake offer anything but a Linux without compromise.
Canonical does everything it can to make the user experience as simple as possible. This includes a lot of under-the hood security fixes, to make it safer (I don't use Ubuntu). At the same time they are distributing a lot of packages a lot of people hold copyright to. A lot of vendors, in other words. If you don't like a package, or a copyright a particular vendor has, you can get rid of that package and/or replace it with one you like better. That is the freedom which Linux offers you.
When you put anything on your computer except what comes with it, you are taking responsibility for what is on it. M$ is selling its OS as something which takes responsibility for your files and so allows you to be ignorant of how it works. Talk to almost anyone who says they prefer Windoze and you will get some variation of "I don't have time to understand what my computer is doing." Of course this means the malware writers have had plenty of time and opportunity to become a big business. Bashing M$ is fun, but even or especially Vista really does make it easier to get infected than to fight it. I'll leave that bald unsupported statement and move on.
The alternative is freedom as in choice. And another way of putting that is freedom as in responsibility. We are responsible for what goes on our computers whether we want to be or not. Most things but not everything works out of the box even with Vista -- the difference when using a Windows system is you are paying someone else to figure out how to make it work for you.
Choice and responsibility are scarier to most of us than we are willing to admit. That's how it is. And that's why most people don't want to use Linux.