How to address situtations where the effort to avoid plagiarism results in less effective communication?

I have been contemplating this topic because of something that happened a number of years ago. Do you have any suggestions on alternative ways to handle the following case:

A student in one of my community college classes (Introduction to Public Speaking) wrote a moving self-introduction for his “icebreaker” speech. The student was a homeless person who had resolved to become a college graduate and his brief autobiographic speech offered the class a rather poignant insight into what it actually meant to be homeless.

The following year that same student was in another of my COMM classes and the students were required to deliver a persuasive speech based on one of the three classic rhetorical modes of persuasion: ethos, pathos, or logos. The aforementioned student’s speech topic attempted to persuade his classmates to help the homeless by appealing to their emotions. A great deal of his speech was clearly “lifted” verbatim from his icebreaker text. To his credit his speech introduction did include the following sentence: “Last year I wrote a speech describing what it means to be homeless and today I would like to revisit that topic.” and he also correctly cited his own speech in the written outline.

When a student just re-uses all or most of a speech without acknowledging the prior work I consider that self-plagiarism. When a student copies verbatim text but gives clear attribution I consider that a lazy effort. However, in this case the precise phrasing and constructions used by the student had such strong emotional appeal I would be hard-pressed to find any way to revise the speech without lessening its impact.

Imagine having Martin Luther King in your speech class and requiring him to rewrite his "I Have A Dream" speech without using any repetitive phrases.

In this case his grade was based on the 2nd speech alone without factoring in the 1st speech in any way. However I did follow up and educate the student on the subject of self-plagiarism (amazing how few students are aware of this concept) and cautioned him to be avoid or at the least to be extremely careful when re-using his work.