Wikipedia defines bigotry here : http://en.wikipedia.org/wiki/Bigot
In a nutshell, bigotry is defined as an unreasonable intolerance of opinions other than one's own.
This seems fair enough, but I sometimes observe the epithet of bigot used in cases where the accused is not necessarily intolerant. For example, one may be called an anti-religious bigot if one opposes religious teaching in government schools notwithstanding that one is himself an adherent of the religion in question. One may be called a homophobic bigot for opposing hate crime legislation involving crimes against homosexuals notwithstanding one's indifference to the sexual orientation of others. One may be called a racist bigot for criticizing rap lyrics and hip hop fashion. One may be called an antisemitic bigot for criticizing Israeli policy.
Some of my conspecifics appear to regard any position as intolerant which does not, in fact, embrace and celebrate the opposing position. It is not enough to accept homosexuality and advocate a society in which folks are free to be as homosexual as they care to be; rather, one has to be willing to declare that homosexuality is a positive good and that it is out of bounds to think otherwise. It is not enough to accept that others have differing religious views and to respect their right to hold and espouse them; rather, one must be willing to declare that one's own religious views are questionable and that all religious views are equally valid. It is not enough to accept differences in "culture" and to defend the right of others to engage in conduct and speech which one finds offensive; rather, one must be willing to declare one's admiration and love for cultural differences of every variety.
To me, tolerance and respect for diversity entail a willingness to live and let live, not an uncritical acceptance and affection for every other opinion or lifestyle. I can be a confessing Christian and tolerate the right of my neighbor to practice Islam without believing that Islam is as correct as Christianity. I can loathe rap music and oversized pants while recognizing that others are free to enjoy these things, and this does not make me intolerant. I can understand why some folks have bishops and a Pope without admitting that such institutions are a good idea. What is "tolerant" about accepting things that you like or agree with? Tolerance is living with things you don't necessarily admire.
On the other hand, some of my wingnut conspecifics insist that tolerance consists in adopting their position whole hog.
Either way, the epithet of bigot becomes a meaningless conversation stopper and is, in my experience, mainly deployed in lieu of reasoning. There should perhaps be something like Godwin's Law governing charges of bigotry in argumentation. Whoever makes the charge is deemed to have lost the argument unless it can be demonstrated that a) intolerance of a point of view has been exhibited, b) that intolerance is unreasonable, c) that the intolerance persists even in the face of valid refutation of the reasons, and d) the bigotry is not self evident.
UPDATE 5/11: Let's call this Jones's Corollary after mick j (see comments).