A group that monitors extremist activity on Wednesday called for the parent company of WordPress.com to shut down Web sites the group says are used by ISIS and al-Qaeda affiliates to publicize “vile” and violent acts, including videos of beheadings and other atrocities. The Counter Extremism Project, a non-partisan research and advocacy group based in New York, said U.S.-based tech companies have been providing crucial infrastructure for the propaganda of anti-American militant groups, often unwittingly.