* Vatican helped prevent single-sex partnership law in Italy * Gays criticise pope's influence in developing world * Campaigner says Benedict competed with Islam, evangelicals By Robin Pomeroy ROME, Feb 19 (Reuters) - Across the road from the Colosseum, the ancient Roman stadium consecrated as a holy Christian site, clients at a busy bar are raising a glass to the pope: toasting the departure of the worst Church leader they can imagine.