Well, you're right about one thing. You're no psychologist!
Seriously though, I think you have a valid argument, and Kasz216 is correct to point to cognitive dissonance as a typical symptom of fanboyism, but I think that is only part of the story.
Take me for example. I don't even own a console and yet I consider myself SDF through and through. I simply prefer Sony's approach to hardware and software to that of the competition (I agree with pretty much everything Mummelman said). I don't need to justify a purchase, and I don't need to filter out good news about other consoles to confirm my preferences. I am perfectly willing to admit that the 360 has a better library of games or that the Wii has better... er... sales. It certainly isn't enough to make me change my opinions.
Before this generation began, I told friends that were considering buying a 360 at launch to just wait for the PS3. I told them the Xbox2 would be another gimped PC in a box, while the Revolution would be a pimped out Gamecube with a Power Glove attached (now with pitch and yaw control!) After they purchased a 360, I would get bomabarded with every bit of bad news about any division of Sony they could find (e.g. the Sony BMG DRM fiasco, exploding laptop batteries). It's not like I own shares in the damn company, I just happen to think they make more rewarding consoles, and yet I constantly found myself under fire for holding such opinions. It was clear that, for whatever reason, there was a massive (and largely unjustified) backlash against Sony. That's why PS fans are referred to as the Sony DEFENSE Force. Sony fans feel the need to constantly justify their beliefs in the face of rampant criticism (admittedly, it's died down a bit now).
I think some people have strong allegiances to a particular console because they just find it difficult to appreciate alternative views. For instance, I CAN easily understand why the Wii's motion controls appeal to mainstream consumers, but I still CAN'T understand how anyone who knows how they work could still be amused by the novelty over a year later.
I also think that people just enjoy the competition. In this respect, supporting a particular console manufacturer is no different from supporting a particular football team. VGchartz exists primarily to fan the fanboy flames by providing statistics to compare against each other. As I've already pointed out, I don't even own a games console, so why the hell would I come to a site dedicated to videogames? For the fanboys of course!*
@ madskillz
What makes you think people that buy a PS3 aren't doing any research? I think ignorant people are just as likely to buy a 360, if not more so. If they did research they would know why the PS3 gets the short straw when it comes to most mulit-platform titles and also why the 360 has more "console exclusives" (the short answer to both of these is DirectX). They would also know that Sony has more internal developers than MS and Nintendo combined and that this is ultimately what will count the most (although Tekken going 360-exclusive would probably be enough to sway me!)
* I'm also a PC gamer. But hardly anybody ever slates the PC (and for good reason).
