Quote 1
They say the fathers, in 1776, signed the Declaration of Independence with the halter about their necks. You, too, publish your declaration of freedom with danger compassing you around. In all the broad lands which the Constitution of the United States overshadows, there is no single spot,--however narrow or desolate,--where a fugitive slave can plant himself and say, "I am safe." (letter.7)
In his letter to Douglass, Wendell Phillips reminds us that even once he was free, Douglass ran a big risk in writing his story: at any time, he could be kidnapped and taken back down South and enslaved. And even though Phillips compares Douglass to the founding fathers (and he compares Douglass's book to the Declaration of Independence), he points out that the American freedom that the Declaration asserted doesn't do much good for a slave like Douglass.
Quote 2
After all, I shall read your book with trembling for you. Some years ago, when you were beginning to tell me your real name and birthplace, you may remember I stopped you, and preferred to remain ignorant of all. With the exception of a vague description, so I continued, till the other day, when you read me your memoirs. I hardly knew, at the time, whether to thank you or not for the sight of them, when I reflected that it was still dangerous, in Massachusetts, for honest men to tell their names! (Letter.7)
Wendell Phillips wants to remind us that Douglass's decision to tell the truth about his experience (and to publish under his own name) is a very courageous one. Even for freed slaves, telling the truth about their lives was dangerous precisely because it was so powerful. Not only would Douglass's enemies try to find him and kidnap him back into slavery, but identifying himself in print made it easier for them to do it.
Quote 3
You remember the old fable of 'The Man and the Lion,' where the lion complained that he should not be so misrepresented 'when the lions wrote history.' I am glad the time has come when the 'lions write history.' (Letter.1-2)
Phillips is reminding his audience of an old fable about a lion who complains that when humans write stories, they always make the lion into the villain. His point is simple: since history books are always written by the winners, the only people who had ever written books about slavery were white people – mostly white southerners who owned slaves. Douglass's book is significant because it's one of the most important examples of a black slave writing about his own experience of slavery.