As an aside, if the murdered killed the guy because he was insufficiently pious (in the murderer’s opinion), I don’t think that qualifies as a sectarian murder. Surely a sectarian murder is one where someone is killed because they’re a member of another sect?
If Catholic A kills Catholic B for advocating for birth control, that’s religiously motivated but not sectarian. But if Catholic A murders Protestant B for being a Protestant, then that is sectarian.
Also, wasn’t there an imam killed in a playpark at night in Bradford or something last month? Was that not religiously motivated then? And a Syrian lay preacher type guy killed outside a mosque in west London?
So I don’t think Islam has much to teach protestants/Catholics about not murdering each other right now.
And vice versa. “We” only just got around to convicting one of the directors of a Christian fundamentalist genocide of Muslims in the heart of Europe. He killed 9,000 Muslims and roamed free for the next decade. Osama bin Laden killed 4,000 Americans and “we” invaded and destroyed the country he was living in (rather than the one that was funding him).