Arguments are probably the best way to get information. An Nvidia Fanboy will dig you the best information about Nvidia and an AMD fanboy will get you the best information about AMD, the more you get the better.
I recon some posts are just plain rubbish and don't even answer one's question. Now, if you we're talking about a fanboy with really little knowledge on the matter, then his posts are going to be misleading, now that would be a problem.
You don't have to gather all your information from a single unbiased person. I don't think fanboyism is a real problem, the problem begin when they start being offensive and arrogant and/or misleading with erroneous data.
Opinions are in human nature and trying to change that, is a bad idea.