This is not a matter of fanaticism, or self justification. It's finding what you like, finding that the company that makes the gear you like just happens to cater to your specific desires, and staying with them because they haven't let you down in the past. Camera gear is not cheap, so faith in the company goes a long way towards justifying a particular purchase.
This is probably true of the majority of people on dpr, regardless of the system they choose. Something about that system meets their needs the best, and it's usually a trademark of the maker. Canon makes killer telephotos with lighting fast AF, and very good C-AF. An action shooter's system. Nikon covers a wide range, from ultra wide to telephoto, and all sorts of pro and semi pro additions. Pentax has those lovely primes.
In the digital field, I gravitated to Olympus. Why? The exquisite lenses. They deliver a 'bit of extra IQ' that I just don't see when I compare my ZD shots to, say, Nikon shots or Canon shots that my friends take. It's minor, but I see it, and I like it. True of all the high grade and super high grade ZD lenses - they really don't make a bad one. Especially true of the HG glass... they perform better than their price might suggest. Haven't been disappointed by one yet.
The one great obstacle was the subpar sensor, less capable than the competition. That's what made the EM5 such a delight - it showed that the problem as compared to APS wasn't so much sensor size, it was the weak sensors they were using. EM5 has a state of the art Sony sensor, and it handily matches the best APS in terms of noise and DR - all it gives up is a few MP that I wasn't really using anyway. If Oly had struck a deal with Sony back in the E3 days, they might still be in the DSLR business.
It's too easy to dismiss people as 'fanboys', simply because they have faith in a certain manufacturer. More often than not, that faith has been earned.
