Macs simply put an end to the plague of viruses, worms and spyware - if you don't install Microsoft Windows.
I do technically agree with you, not being a Wintel-Only type myself. I just do not think every single opening should result in a sales pitch, whether someone posts a Mac answer, or a picture of a Penguin.-And there are those types of evangelists around.
The Clueless are still capable of bringing down a Mac, or getting A Linux system rooted, but yes, they are helped out a lot, since everyone is going to write malicious code for the most popular system.
Windows boxes are also prone to Operator wetware failure, and are only one multiple Real Media installation from becoming useless.
The reason Macs dominated Graphic Arts till recently was because they started the Plug and Play reputation amongst non-geeks back in the 80's.
That said, I have not seen a blue screen in years and years. But I am rather geeky, going back to FORTRAN IV.
I know, I know...
"Nobody runs the Steam Loom like Big Mike!"
Plug and Play was a factor, but not the main one. I would attribute it to some different things - The 68000 architecture was better than the 8088 for graphics - it could address more memory, it had better registers and a better instruction set. The Windows GUI was incredibly primitive compared to Macs, especially with Apple's patented QuickDraw technology. And I remember plenty of MS-DOS users who openly disparaged the mouse, and swore they would never use one - but a mouse is very handy for GUIs and graphic design.
Today, the Mac is no longer relegated to niche markets. It's an excellent general-purpose computer, ideal for the typical user.