“Did I hear that wrong, or did he take a major slap at slavery?”
He took a major slap at the King of England.
Jefferson’s philippic against slavery was not included in the Declaration of Independence for reasons explained in his contemporaneous notes.
He has refused his Assent to Laws, the most wholesome and necessary for the public good.
It is true that Americans(then British Subjects) viewed slavery as un-wholesome, and they viewed abolitionism as a public good.
It is also true that the King refused his assent to America's abolitionist laws by purposefully vetoing those laws or having his creatures commit the veto.
It does qualify on both sides of the listed grievance. There were much large issues at play and many other vetoed laws but it would be incorrect to wipe slavery out entirely. That would not be within the spirit of 1776.
“Jefferson’s philippic against slavery was not included in the Declaration of Independence for reasons explained in his contemporaneous notes.”
I can’t believe I never heard this before.
All I can say, I guess, is “duh.”