Doesn’t matter the religion. There are extremists to be found, and they need to be ostracized, outed, and in some cases arrested when they engage in violent acts or spur others to act violently:

Burning of Christian churches in Israel justified, far-Right Jewish leader says http://t.co/ewVcEixFcw pic.twitter.com/FEn60LbBwh

— The Telegraph (@Telegraph) August 6, 2015

This is abhorrent stuff, and if you swap out the religion, it could apply to pretty much any religious group - though most in the US would identify the extremist as Muslim (thanks Islamophobia). Yet, extremists here who are willing to engage in violence - like against Black Churches - would also consider themselves Christians.