The rebellion was in equal part a protest by feudal lords against the intrusion of central government into their domains ; a conservative Irish reaction Response to English policies that were altering Change traditional Gaelic society ; and a religious conflict Hostile_encounter , in which the rebels claimed Statement that they were upholding Catholicism against a Protestant queen who had been pronounced Statement a heretic in 1570 by the papal bull `` Regnans in Excelsis '' .