Why shouldn't someone feel bad if they have never heard this before?
No one should feel bad, because even Peter—who spent three years with the Lord Himself and preached from Pentecost filled with the Holy Spirit—acknowledged by inspiration that some things in Paul’s epistles are hard to be understood, so much so that he could not comprehend them.
Les explains that when people come with questions and say they have never heard these things before, he tells them not to feel bad. Peter had spent three years with the Lord Himself and had preached from Pentecost on, filled with the Holy Spirit. Yet after Paul came on the scene and wrote his letters, Peter still, by inspiration, had to admit that much of what Paul wrote he could not comprehend. Peter says these things pertain to salvation, and in them are some things hard to be understood—especially for Peter as a well-founded, indoctrinated Jew. The passage goes on to say that the unlearned and unstable twist these things, just as people have twisted the Scriptures ever since Peter wrote, making them fit what they think they should say.