I'm afraid I don't really know how to respond to subjective opinions unsupported by hard evidence. But I see this happening all the time, particularly on forums such as dpreview.
It's rather ironic that dpreview is one of the few sites that provides in-depth technical reviews of equipment, yet their forums seem to be full of mindless bickering on mattters obscured by ego.
There are some who are happy to accept the opinion of any 'so-called' expert, probably because they are not confident in their ability to understand the issues.
This doesn't only apply to the choice of cameras. It's a wide-spread phenomenon that advertising companies thrive on. When Pat Cash retired from tennis, he got a bit short of cash and was persuaded to advertise underpants. The company selling the underpants obviously figured there was a large number of people out there who would be influenced by Pat Cash's choice of underwear. (If this underwear is good enough for Pat Cash, then it's good enough for me. It might even improve my tennis.)
A similar situation has now occurred in this thread. A professional photographer (SecondFocus) has claimed that the E-3 produces better images than the 5D. There's an implication that any opinion from a prefessional must be gospel and no evidence is required. Now that's completley ludicrous in my opinion.
At the same time, I recognise that there are lots of people in this world who are prepared to accept without question any opinion from an 'expert', whether such expert is a professional photographer, a doctor, a scientist or a priest. (Or a CIA agent).
However, I'm not one of them.