He describes as "racist" in "describing the slaves themselves as 'obtruding' upon and threatening the lives of the colonists". Oddly, for an English professor he misses the grammar. His need to decry Jefferson as racist overwhelms his grammatical judgment; that happens a lot with sufficient motivation. Let's assume he was just in a hurry and not willfully blind.

Slaves weren't obtruding upon; Jefferson describes the wrong in King George's having "obtruded them" upon the colonists. That strikes me as specious, but the goal here wasn't to condemn the slaves--after all, they're described as men who were wronged--but the King.

As for the slaves being culpable in threatening murder, King George "is now exciting those very people to rise in arms among us." That's rather a different proposition. The agency is again not the slaves, but the King. And, in fact, there were attempts at fomenting rebellion in areas that were pro-independence, and threats to declare slaves free and encourage them to rise up in open rebellion--which would include armed struggle against the same colonists the British would be fighting--if the colonists dared to hurt the King's representatives or arch-supporters or declare independence. The same threats were made concerning inciting insurrection among the Indians.

That said, I continue to fail to understand some of the complaint, though. While I get the threats of mayhem, and I can get "obtrude something" to mean "push something forward" in some contexts I can't get rid of the generally negative connotation in this context. You don't obtrude tiramisu on a customer who wants to buy it. Perhaps a pusher obtrudes meth on an addict, having gotten him addicted? In any event, Jefferson was a slave owner. The best I can come up with is that he didn't see how much resistance there would be to saying enslavement was one of the King's crimes and wanted to give the Congress a way out, of denying blame for what they'd willingly done (bought and sold people). Even that's so stretched and contorted as strain credulity.

<snip>
"Like so much in the American founding, these lines are at once progressive and racist, admitting the wrongs of slavery but describing the slaves themselves as “obtruding” upon and threatening the lives of the colonists. Not surprisingly, this complex, contradictory paragraph did not survive the Declaration’s communal revisions, and the final document makes no mention of slavery or African Americans."