There are certainly more than quite a few "Christians" who've done such heinous things in this country. Beyond the mosque burnings of the past decade or so, there are certainly a few other "mass" events in this section at least, such as the torching and bombing of quite a few black churches by the Klan and others of their ilk. Many of said events justified by particular interpretations of Christianity.

I think the roots are more social and political than anything inherently religious. There certainly weren't these amounts of anti-Muslim protests in the US until after the political event (terrorism is politics carried out to an extreme, some might say) of 9/11. There certainly weren't as many flag burnings, bombings, etc. before political events of the 20th century in the Middle East and North Africa.

Yet the result is a bunch of aggrieved people who feel that they have to get "revenge" for what others have done. A true crisis of modernity in which the "opiate of the masses" is heated and melted to mold into whatever contours are required by their adherents in order to deal with their frustrations, anger, etc. It is no accident that certain sectors of Christianity rail against evolution, secular society, and competing faiths. Same holds true for certain sects of Islam in that in a world where believers are besieged by political, social, and scientific events that threaten their worldviews that some will turn to violence.

The forms of this reaction may vary based on group standing in a larger society (after all, some form of Christianity or its remnants is dominant in the US and Europe while quite a few Muslims are not yet allowed to be fully integrated into Western societies - or some choose themselves not to become assimilated), but to claim that one is the "fringe" and the other "the center" is a specious claim. There's a bit more commonality than that and that is why I linked to that story, because the motives are not that dissimilar.