France shows Oz how to deal with a siege, page-62

This man murdered 77 people, mostly teenagers, and maimed many others in 2011.

"On the day of the attacks, Breivik electronically distributed a compendium of texts entitled 2083: A European Declaration of Independence, describing his far-right militant ideology.[11][12][13][14] In them, he lays out a worldview encompassing Islamophobia, support for "far-right Zionism"[11] and opposition to feminism.[15][16] The texts call Islam and Cultural Marxism "the enemy", argue for the violent annihilation of "Eurabia" and multiculturalism and advocate deportation of all Muslims from Europe based on the model of the Beneš decrees.[17][18] Breivik wrote that his main motive for the atrocities was to market his manifesto." (http://en.wikipedia.org/wiki/Anders_Behring_Breivik)

Should we be concerned about others who share his ideology?