Police in Italy arrested an Italian man in the slaying of a Nigerian vendor whose brutal beating death on a busy beach town thoroughfare was filmed by onlookers without any apparent attempt to intervene physically. Video footage of the attack has circulated widely on Italian news websites and social media platforms, eliciting outrage as Italy enters a parliamentary election campaign in which the right-wing coalition has already made immigration an issue. “The murder of Alika Ogorchukwu is dismaying,” Enrico Letta, the head of the left-wing Democratic Party, wrote on Twitter, naming the vendor …