DesignCaddy - you ask why? My theory is that it's because they are a minority, and people in a minority tend to feel they have to defend their corner. It seems to be a human instinct thing.
As for the debate, PC/Mac are both the same these days...they both crash, they both cost money, they both keep me in work
More seriously - it used to be true that Macs were far superior for graphical design works, it used to be true that Macs were much easier to use, it used to be true that they looked much better than ANY PC (now it's just better than most), and it used to be true that there was roughly the same total cost of ownership for companies for both PCs and Macs.
Now, PCs are up to the graphical intensive tasks, especially because most of the load is taken by the graphics cards and these are the same or similar on both platforms.
Now Pcs have become almost consumer level devices with the advent of XP, and Macs have become trickier (under the hood) thanks OSX being Unix in all but name.
Now some companies making PCs have concentrated on making sexy looking machines as well as performance/price...and there are all sorts of options to customise them yourself if looks are important to you.
Now, because PCs dominate the market so much, and most people develop PC skills (both users and support staff) etc, most companies find the TCO for PCs significantly lower than for Macs (we've just had external KPMG auditors looking and reporting on this for where I work and they have the business studies to back this up).
Which would I pick (having used both and many other platforms in the past)? An Acorn Archimedies any day