It's easy to point out fanboys we disagree with. A better mental tool might be reflecting upon yourself and finding out what you might be a fanboy of, what are you irrationally attached to that you will defend vehemently, even when at odds with reason?

Once you discover the object of your irrational affection, try to sympathize with those irrationally at odds with it (i.e. haters, detractors, bashers, the Other fanboy, etc.)