LONDON — Media titan Rupert Murdoch and his son James defied the British Parliament Thursday and refused to appear next week before a committee investigating phone hacking and bribery by employees of their newspapers. The committee said it had issued summonses to the Murdochs, setting up an extraordinary confrontation between one of Britain’s most powerful men and a Parliament once seen as easily bent to his will. The Murdochs’ refusal was a dramatic snub of a body that forced them to abandon their ambitions of purchasing highly profitable network British Sky Broadcasting Wednesday after lawmakers from all parties united to demand that Murdoch’s News Corp.