Intolerance to religion, political views, other people's opinions, personal beliefs or culture is often the root cause of conflicts around the world.
In recent years, Isis (Islamic State of Iraq and ash-Sham), a jihadi extremist militant group, has come to symbolise intolerance.
It follows an extreme interpretation of Islam, promotes religious violence, and regards those who do not agree with its interpretations as infidels.
They probably believed they were taking a stand against extremism but, in reality, they were using the same tactics the militant jihadists use to intimidate those who do not share their beliefs.
It uses brutality, including beheadings, to intimidate local populations and has released a series of propaganda videos aimed at Western countries showing these horrific acts.