One of these requirements is for the teacher to be "soaked" in both the New Testament and the dogmas of the Church. To give an example of how important this soaking is to our catechetical and evangelistic work, he mentions the apologetic in response to Jesus' shocking words to Peter. This is what the Catholic Evidence Guild use to give when people would try to use "Get behind me Satan!" as proof against the authority of Peter. Sheed provides some excellent insight as to the root of the problem as far as these words from Jesus are concerned. I would like to provide it here:
Take again — as a sort of combination of being soaked in dogma and soaked in New Testament — the famous objection of the street corner heckler to the infallibility of the Pope, that "Christ called Peter Satan." In our early years on the platform, we gave a thoroughly unsatisfactory answer to the question, an answer we had got out of the books. Our answer was this: Christ did say to St. Peter: "Get thee behind me, Satan"; but, we said, the context explains it. Our Lord had told the Apostles that He must go to Jerusalem to suffer and die. Peter, out of his love for our Lord, begged Him not to do so, and our Lord then said to Peter: "Get thee behind me, Satan"; and we explained that the word Satan means tempter and that Peter, out of love of our Lord, was tempting Him not to go through His suffering. And all this was very much to Peter's credit. That was our explanation and it never satisfied the crowd. Why? Because we had explained the words, but we had not explained the violence of the words. Satan does mean a tempter, but Satan means Satan: our Lord knew it, and Peter knew it, and it was a scarifying thing for our Lord to have said to Peter. Why the vehemence, if that was all? Go forward to the Agony in the Garden and you see more profoundly. Our Lord asks His Father the very thing that Peter had suggested to Him. "Don't make Me go through with this suffering." And our Lord feels the anguish of it, so that the sweat runs off like blood. Now, that sweat as of blood is the measure of the temptation that Peter is exposing our Lord to, when he begged Him not to suffer and die. And once you see the sweat as of blood, then you understand the vehemence of "Get thee behind me, Satan."What Sheed is telling us with this and other examples is that it is not enough to simply know what we believe about something. We have to be able to get to the heart of the teaching, and to the heart of the problem that the objector sees in the teaching. As apologists, we can't just downplay the alarm that people have over Jesus' response to Peter. We have to give that alarm the respect it deserves as a valid response and then respond honestly to it.
For further apologetics on this issue, see this article.