This one is tentative. It looks to me like a possible example of the BBC ascribing moral equivalence to two sides that are not morally equivalent, at least not recently. However I do not know much about the history of the two communities involved, and I am open to correction.
In Pakistan fifteen Shia Muslim worshippers were murdered at prayer almost certainly by a Sunni Muslim suicide bomber.
The BBC says,
The communities have a history of violence.
On 2 March, Sunni radicals killed more than 40 people and wounded 150 in an attack on a Shia procession in the south-western city of Quetta.
Last July an attack on a Shia mosque in Quetta left around 50 dead.
I don’t need telling that the Ayatollah Khomeini was a Shia, or that Sadr is a Shia. Shia fanaticism certainly exists. Nonetheless I see no warrant for the bit about “the communities” in Pakistan having a history of violence: all the examples cited are Sunni terrorism against Shias.
Indeed, the very group (Lashkar-e-Jhangvi) that claimed responsibility for an earlier massacre of Shias is also suspected of the Church bombing in January. Not for the first time, I don’t think this is a “cycle of violence” at all: it’s a group with links to Al-Qaeda and the Taleban killing randomly chosen adherents of any religion or denomination they don’t agree with.