I don't know if you're still being facetious, but that is without doubt one of the most ridiculous statements I've ever heard.
I'm only being facetious in as much as I'm stereotyping all Linux users as being of one type. I'm sure everyone who uses it has their own reasons.
People who use Linux are simply people who prefer to get work done, without the operating system getting in their way, or automatically rebooting their PC after an "automatic update", because you stepped out of the apartment for a few minutes to pick up some groceries. Linux is the OS for people who simply want technology that works and stays out of your way, not interrupting you every 5 minutes, because it can't decide on its own whether it should let "CreditCardThief.exe" access your address book, or let "KeyLogger.exe" connect to the Internet.
I run XP. I have automatic updates turned off. I have the firewall turned on. It neither reboots my PC, nor asks me if I should allow applications to access the internet, with the exception of the first time an app that needs to access the net runs.
Also, just how much work can you get done when the tools and APIs you need aren't even available for your OS? I mean presumably even if you're using Linux to write the game, you do plan on making money on it, and so have no choice but to make it work with Windows. How are you gonna make sure it works nice with Vista's user access controls, or its sound system, or that your code even runs fast on it? Reboot into Vista every 30 minutes to test your code? That sounds like a real time saver.
If you're going to all the trouble to use Linux because Vista has a few annoying features, WHICH YOU CAN DISABLE, then that's just downright foolish.
The reason you check MD5 hashes (or even better, SHA-1 hashes or GPG signitures) , isn't to ensure the file was transfered correctly, but that it wasn't maliciously modified, by say a man in the middle, trojan injection.
Paranoia, pure and simple. One's chances of being a victim of such an attack are one in a million. You have a better chance of being killed in a car crash. That doesn't stop you from enjoying the convenience of the automobile though, does it?