As to offending us, Nephi assures us we will only be offended by his plain, sometimes blunt, talk if we are listening to the Devil. "And it speaketh harshly against sin, according to the plainness of the truth; wherefore, no man will be angry at the words which I have written save he shall be of the spirit of the devil. I glory in plainness; I glory in truth; I glory in my Jesus, for he hath redeemed my soul from hell." (2 Nephi 33:5-6.) Anger is how Satan gets us to stop listening. If Nephi's words anger you, then you should consider carefully why.
He wants us to realize taking offense at words intended to bring to us eternal life is a gross mistake. If we do that, we have been deceived. And we cannot be deceived without surrendering to the adversary, who intends to bring about our destruction.
We come to the end of Nephi's commentary and exposition on his intent to warn and guide us. This statement of intent allows us to see why the Isaiah passages were selected by him. They foretell of our day. They echo the same themes as Nephi's cautionary warnings. They are useful to Nephi in order to set out in prophetic verse the things which he saw but was commanded not to write. The Isaiah materials in Nephi's text need to be read with these themes in mind.