The 'reason' I 'd call it religious is because people tend to be black&white about it, as in "there can only be one".
I started out with my Amiga as the first 'real' OS, 'had' to switch to windows; have been dabbling with Linux on and off and only know about Apple indirectly.
=> I actually was anti-MS-DOS/Windows up to Windows 2000, as from there the OS became stable & usable IMHO.
At the time, my job involved MS products (and it still does) so the choice between Wintel and Apple as alternatives to my Amiga was quite simple. On top of that, Apple is/was way too expensive anyway. Linux was too much niche at the time and slackware looked impressive but couldn't convince me at the time. BeOS seemed fun but I never got around getting one.
=> By now I know Windows 'pretty well', in each case a lot better than Linux. I'm sure I can complain about a lot of things that are 'wrong' in linux that someone with finer understandings about the OS would be able to fix in minutes. Experience shows the opposite is true too.
in fact, over the years, I've suggested and installed Ubuntu on several machines of friends that only use them for basic web & office stuff. They always start out with wanting Windows because that's what everybody has -- so yes, it probably IS a cultural thing -- then again they always assume Windows is free and 'know a guy'. I've stopped supporting those installations as they're a death-trap because Windows Update refuses to serve them updates and frankly, I can't blame MS. People spend 1000$ on the latest hardware but refuse to shell out a single cent for the OS, sigh. Anyway, when return them their machine with Ubuntu on it they hardly realise they're using something different because in the end it all looks and feels alike. (even with the default settings.. disclaimer, that was before Unity so far everybody seems to be happily churning along with their 'old' versions... it's not only XP that still works).
Anyway, please don't dismiss me as a Windows-nut, I am not... but I do hate it when people come by and start bashing on Windows because of things that are quite in the past. You don't hear me complaining how Linux has lousy driver support although yes, I've spent plenty a night getting things right only to have the next update mess it up again.
PS: another reason why I'd risk calling these discussions religious is because people tend to bring in words like 'Evil'. MS isn't evil, it's just a big company that tries to make (more) money. Same goes for Apple & Google & ... well, all of them I guess. And that includes RedHat and Agile and ... it's capitalism at work. It may start out with a couple of guys having a good idea, but it always ends with highly overpaid 'executives' that simply try to squeeze the most out of the client-base.
All in all, maybe (probably) Windows *IS* more susceptible to viruses than the other OS's. Personally, I think not although it does require some common sense from the user, true. These OS's (and software in general) are way too complex with way too many variables interfering which each other. Maybe we'll get there someday and have some kind of background AI that warns us against potential threats [Clippy: it looks like you;re trying to install a screensaver] but I very much doubt I'll live to see it. That said, it obviously gets more difficult over time so there IS hope; but as people expect new features with each never new version released there's bound to be some new vulnerability being introduced. I'm pretty sure Pown2Own is only the tip of the iceberg and there are plenty of smart people around that know how to circumvent the safety mechanisms.. In way that's a waste of talent but I guess everyone has bills to pay so who am I to judge.