The correct answer is Gullible.
The speaker means to denounce the rule of God over christians by describing these individuals as peons with inmaculate spirits and obeyous solely to the will of their ruler. This is also evidenced by the speaker's uncertainty encountered in the statement "... God has given them spirtual freedom.", referring to the Christians spreading of their religion; activity which Christians believe comes from their choice alone, but it is rather commanded by their God.