How does Douglass portray the Fourth of July?

In his speech, "What to the Slave is the Fourth of July," Frederick Douglass portrays the day as unique in that it means different things to separate segments of American society. Depending on whether one is a free American or a slave, the Fourth of July can mean either pride in a national accomplishment (American independence from the English) or sorrow in a national travesty (the practice of slavery within American borders).
Douglass says that, for white Americans, the day is one of "joyous enthusiasm," a day made possible only because men "preferred revolution to peaceful submission to bondage." For black Americans who are slaves, however, the Fourth of July is a day of "mere bombast, fraud, deception, impiety, and hypocrisy." Douglass argues that slaves cannot fully enter into the joy of the day because they haven't yet been released from the shackles that oppress them. He cites the example of the slave trade in the Southern states.
There, whole families are still sold like cattle; Douglass bids his listeners to picture what happens all too often at slave auctions in America:

I will show you a man-drover. They inhabit all our Southern States. They perambulate the country, and crowd the highways of the nation, with droves of human stock. You will see one of these human flesh-jobbers, armed with pistol, whip and bowie-knife, driving a company of a hundred men, women, and children, from the Potomac to the slave market at New Orleans. These wretched people are to be sold singly, or in lots, to suit purchasers. They are food for the cotton-field, and the deadly sugar-mill.
Attend the auction; see men examined like horses; see the forms of women rudely and brutally exposed to the shocking gaze of American slave-buyers.

So, Douglass maintains that the Fourth of July is a day that reveals to the slave, "more than all other days of the year, the gross injustice and cruelty to which he is a constant victim." From the viewpoint of the slave, the day is a "sham" and the "boasted liberty" of free Americans, an "unholy license" to continue the slave trade. He also argues that the supposed "national greatness" is nothing but a "swelling vanity" and the "shouts of liberty and equality," a "hollow mockery" to those who are still enslaved. He encourages his listeners to consider the fact that the Declaration of Independence should apply to all Americans, both black and white, and that the "Constitution is a GLORIOUS LIBERTY DOCUMENT" which will never support the practice of slavery.