Linux is Unix, which means it's crap. Unix was originally invented so some guys at Bell Labs (At&T, who's definantely anti everything fun). Besides, Linux is licensed under the GPL, which is so Communist it makes Lenin look blue by comparison. Of course, he's dead, and probably pretty cold which doesn't help his complexion.
There's no real security in Unix type systems anyway. Just go look at the number of bugs listed for "unix" on bugtraq and compare it to a nice secure OS like Windows 2000. Besides, Linux makes you use (gasp) a command line. Us civilinized types got rid of those back when we switched to Windows. They've been playing with something called 'X' for years, but I've been informed by my cop friend that it's a drug, and illegal, so you shouldn't mess with it.
There's no Plug and Pray support, so you'd actually have to know something about the computer you're working on. Who gives a rat's butt about that? I mean come on....it's not like I want to dig around the manuals to find out what they heck this crap is, it's just supposed to work when I turn the thing on.
You have to "log in". What a load of crap. what happens if I forget my password? Oh, I have to do what? Single user mode? Isn't that how I use it already?
In short, I think it best is summed up by this quote from the "Unix Hater's Handbook":
"I have a natural revulsion to any operating system that shows so little planning as to have named all of its commands after
digestive noises (awk, grep, fsck, nroff)."