It sounds as though Mr Jenkins's focus has evolved a bit over the past few years; when he wrote this article in the New Republic, he wasn't exactly saying that Western evangelicals were irrelevant to Ugandan homophobia. It was more that such influence had been over-emphasised. He situated African homophobia in the rising tide of evangelical Christianity in Africa, and noted that first- and second-generation converts to any faith tend to be more literal in their interpretations of its holy texts.
He did argue that competition between Christianity and Islam helps drive homophobia, but he did so in a way that highlights how values are shaped dynamically by the discourse generated in religious competition, including missionary discourse. He also placed African antipathy to homosexuality in historical context, recalling a fascinating angle to the history of Uganda's 19th-century Catholic martyrs. (Apparently some of them were Christian pages who refused to take part in the pederasty adopted by the Arab-influenced Muslim king of Buganda.) "For many Africans," Mr Jenkins wrote, "sexual unorthodoxy has implications that are at once un-Christian, anti-national, and oppressive."