A BIGOT is "strongly partial to his own group, religion, race, or politics and is intolerant of those who differ." A Christian, for example, who is intolerant of anyone who is not a Christian, is a bigot. Or anyone who is Chinese and intolerant of anyone who is not Chinese, is a bigot.
If the group to which you are partial is your race, then bigotry is the same as racism. There are definitely people trying to stop Islam's relentless encroachment who are motivated by bigotry. But criticism of Islamic doctrine is not bigotry.
Criticism of Islamic teachings is simply religious criticism, which is a perfectly legitimate and worthwhile thing to do in a free country. If I told you that in Buddhism they believe the source of human suffering is the grasping nature of the mind, is that bigotry? Even if I said I think that might be too simplistic and that there may be other causes of suffering, is that bigotry?
No, that's simply discussing religious texts.
And if I say the Quran says (91 times) that Mohammad is a good example of human behavior, is that bigotry? No. Even if I say I don't like that because the historical records of Mohammad's actions aren't something I want to see emulated, is that bigotry? No. We're just talking about a religious text and history.
And if a Muslim says he believes Jews are evil and should be destroyed, is that bigotry? Yes, it is. But what if he says "it must be true, it says so in the Quran," is it still bigotry? Yes. And if I say I don't like that about the Quran, is that bigotry? No. What if I say all Muslims are evil, is that bigotry? Yes. Get the difference?
The reason it seems to many people that anyone criticizing Islam is a bigot is because some bigots have, in fact, criticized Islam. But criticizing Islam, or any religion, does not make anyone a bigot.