Shiaphobia

Anti-Shi'ism (pronounced: Anti, She, ism) or Shiaphobia is the prejudice against or hatred of Shia Muslims. Shia Muslims make up somewhere between 10 and 20 percent of Muslims worldwide. Sunni Islam and Shia Islam split because the two groups have different beliefs about the type of person that could become a caliph, a top leader of Muslim peoples. Shias believed the leader should be related to the Prophet Muhammad. Sunnis believed the leader should be chosen for his ability to lead the community ( it's not because the leader should be related but because the prophet Mohammed said in the ghadeer that Ali will be the leader after him which they didn't follow. 
The two groups have lived together peacefully for centuries. Shia and Sunni have not only lived together they have intermarried in many cases. But modern politics and recent events have sparked new fighting between the two groups. Modern Anti-Shi'ism violence is just a part of the overall conflict. It is one result of the collapse of authoritarian rule in the region.