fought.'
author:
- |
    Alexandra Olteanu\
    IBM Research\
    alexandra.olteanu@ibm.com\
    Carlos Castillo\
    UPF, Barcelona\
    chato@acm.org\
    Jeremy Boy\
    UN Global Pulse\
    jeremy@unglobalpulse.org\
    Kush R. Varshney\
    IBM Research\
    krvarshn@us.ibm.com\
bibliography:
- 'ref.bib'
title: The Effect of Extremist Violence on Hateful Speech Online
---

Introduction
============

Hate speech is pervasive and can have serious consequences. According to a Special Rapporteur to the UN Humans Rights Council, failure to monitor and react to hate speech in a timely manner can reinforce the subordination of targeted minorities, making them “vulnerable to attacks, but also influencing majority populations and potentially making them more indifferent to the various manifestations of such hatred” [@izsak2015hate]. At the individual level, people targeted by hate speech describe “living in fear” of the possibility that online threats may materialize in the “real world” [@awan2015we]. At the level of society, hate speech in social media has contributed to fuel tensions among communities, in some cases leading to violent clashes [@izsak2015hate].

Following one of the most severe humanitarian crises in recent history, Europe has seen a high immigration influx, including Syrian, Afghan, and Iraqi refugees.[^1] In the same period, several deadly terror attacks have occured in Western nations [@reuters-attacks-Europe; @global-terrorism-database], leading to an increasingly alarming 