"You are trying to say that users needing to type chmod +x ./latest_flash_player_youtube.sh , is sufficient protection to prevent end users from running things they shouldn't.... "
I did not actually say that, but it is probably true. Most users are either a) smart enough to realize they do not actually want to do this or b) not actually capable of pulling it off without help (hopefully, from someone who belongs in category a).)
However that is NOT what I was saying. The exploits we are discussing rely on Win32 executables, NOT SHell scripts. Even if the user manages to slide in between case a) and b) somehow, setting an executable bit on a win32 application will not magically make it work on *nix. You would need to also install WINE and do some intricate configuration magic with it before this would work.
"Ransomware is not prevalent in Linux, but again, it is absurdly naive to think that it couldn't"
Notice I explicitly agreed with you that it could be done.
"Again, end user education is key, regardless of OS. Implying to under-informed users that OSX is magically secure against cryptoware, is a recipe for disaster."
Yes and no. Certainly end-user education is key, regardless of OS. And certainly it's true that no OS is magically secure against malware. And I think it's correct to say that the OS does nothing to prevent it. But that's looking at it backwards.
What OSX, and *nix systems in general, should get credit for is not that they *do something to prevent infection* but that they do *less to facilitate infection*.
Of course, the same things that make Windows an extraordinarily easy target for malware also makes it an extraordinarily easy target for more legitimate programming as well.
And that, ultimately, is why it was designed that way. Developers, developers, developers! Windows is ultra-friendly to developers, it goes out of its way to make life easy for them, and guess what? A subset of those developers make malware. And the same things that makes Windows easy for one set of developers makes it easy for the other.
OSX actually deserves some kudos because it *does* make development a little harder here and there, for the benefit of the user. And while saying OSX is 'virus-immune' would be clear BS, saying that it's an effective way for a technically challenged computer user to dramatically reduce their risk of being infected is actually true.
Linux can be deployed to even better effect on the security front, of course, though I would not recommend it for the technically-challenged unless said user has a friend or family member to help with setup and ssh in occasionally to administer it.