You are correct, but including the issue of slavery was given consideration as one of the reasons for breaking away from England. Here is the passage deleted from the final Declaration of Independence. This was written by Jefferson.
“He has waged cruel war against human nature itself, violating its most sacred rights of life and liberty in the persons of a distant people who never offended him, captivating & carrying them into slavery in another hemisphere or to incur miserable death in their transportation thither. This piratical warfare, the opprobrium of infidel powers, is the warfare of the Christian King of Great Britain. Determined to keep open a market where Men should be bought & sold, he has prostituted his negative for suppressing every legislative attempt to prohibit or restrain this execrable commerce. And that this assemblage of horrors might want no fact of distinguished die, he is now exciting those very people to rise in arms among us, and to purchase that liberty of which he has deprived them, by murdering the people on whom he has obtruded them: thus paying off former crimes committed again the Liberties of one people, with crimes which he urges them to commit against the lives of another.”
It was in Jefferson's original draft. The other members of the committee wisely struck all that out of the document. Instead was left in a comment about the King's men provoking slave revolts, so it ended up with a mildly pro slavery statement in it.
But let us not underestimate the influence it had later on greatly expanding the abolition movement. Those five words "all men are created equal" exerted far more power on the subsequent direction of the country than the lament about the King's men fomenting slave rebellion.
I am convinced that Jefferson almost singlehandedly launched the abolition movement into the dominant force which it eventually became.
Had those words not been put in there, I think much of what happened in terms of abolition, would not have happened as it did.
I believe I know of one signer of the Declaration, that upon contemplating those words for time, eventually decided to free his own slaves.
But as I said, that wasn't the document's purpose when it was created, despite the fact that Lincoln made efforts to mislead people that it was with his "four score and seven years..." speech.
The thesis of the Declaration is that states have a right to be free, which is pretty ironic since Lincoln was commemorating an occasion in which the battle was won by the forces trying to subjugate a collection of states that wanted independence.
Interesting discussion, all.
Bookmark for future rereading and reference.