"Ah, maybe you have a crap printer unit that is only supported on Windows by the manufacturer and they don't publish full specifications to allow others to do so? Did you complain to Brother about this? Otherwise what do you expect, just smile and pay MS for your bad choice."
Whilst the underlying point about manufacturer support for different OSes is correct the attitude with which you put the point across is what really shits me about some Linux advocates - it may not have come across how you intended but it reads as patronising.
I use a variety of different OSes and what people need to realise is:
1. Most people know jack-shit about computers. They want to access the internet, their mail, photos etc and for things to just work. Perhaps they'd be better suited to an appliance type of device such as an iPad but that's a different matter.
2. The printer and other peripherals they have aren't "crap", they're just what they happen to have and they don't wish to be patronised about their choice but assisted in getting it working. Most people look at a printer from the angle of "does it do photos, colour documents, and what does it cost etc" not "what drivers are available" or "is it supported out of the box by kernel 2.6.x-y..." because they don't have the knowledge to realise that it may not be supported.
3. If things work when you use the Live CD then why the f*ck can't they just work once the operating system is installed - wireless connections on Ubuntu being a case in point. Several times for me in fact. This is probably what gets a lot of users.
4. Be aware of how you advertise things - if Linux is promoted as easy to use then there will be great expectations placed upon it from a usability perspective and it just isn't there yet. If you want to know where/what/why then just compare using the OSX interface to your favourite desktop.
I get things working eventually because I'll search on forums and post questions (and solutions when I've found them to assist others) but I also recognise that the average user has neither the aptitude nor patience to go through what I have at times to get things working.
Hell, I'll probably be flamed downwards but I'm prepared to acknowledge what others go through rather than just tell them their kit is shite and go use windows.