How can one discuss with someone who argues that "the Ummah of Muhammad (peace be upon him) is blessed with mercy" as a reason for not accepting religious advice?

The words of this man are truth by which falsehood is intended; for he desires to escape from religious obligations. This is from the cunning and adornment of Satan. The Prophet, peace and blessings be upon him — whose past and future sins were forgiven — was the most pious of people towards his Lord, the most obedient, and the most fearful of Him. He used to stand in prayer at night until his feet would crack, and he would say: "Should I not be a grateful servant?" The best of creation after him were his Companions, and they were the most eager of people in obeying Allah, the most hastening to His pleasure, and the most distant from what displeases Him. Therefore, hope in the mercy of Allah Almighty should not lead a person to neglect their duty towards Allah, the Exalted and Glorious.