Final answer:
The most clearly shown element in the excerpt is sentimentality.
Step-by-step explanation:
The most clearly shown element in the given excerpt from Frederick Douglass's autobiography is sentimentality. Sentimentality refers to the expression of tender or emotional feelings in a way that evokes sympathy or sentimental reactions from the reader. In this excerpt, Douglass expresses his early sentiments and the emotional impact of not suppressing his opinion. He conveys an emotional connection to his beliefs and values, which is indicative of sentimentality.