Why do you think Douglass begins part of his introduction this way? What contrasts is he trying to make between himself and his audience?

Douglass introduces his speech that way because he wants to shock his audience strongly. He is trying to show how hypocritical his audience is by celebrating the freedom he and his fellow men do not have.

Explanation:

Douglass began his speech by showing with the celebration of American citizens that it is contradictory, petty, lying and hypocritical. He uses words that refer to these adjectives and question the real meaning of American values so sacred and respected by all.

Douglass wants to show his audience that this freedom exists only for a select group of citizens. Blacks, like him, cannot celebrate it because they recognize that they are deprived of it, so that freedom does not exist. However, whites continue to ignore the ideological "prison" of blacks and celebrate American ideals as if they encompass the entire population.

Explanation:By "sacrilegious," he means the evil defilement of sacred American ideals - democracy, freedom, and equal rights. The real subject of his speech, he concedes, is American slavery. He condemns America for being untrue to its founding principles, its past, and its present