“You really must show me your copy of this document. I can’t find the words slavery or slave anywhere in it.”
See: “He has excited domestic Insurrections amongst us . . .”
Are you arguing that the country was founded to help preserve slavery? That sounds like the argument that someone would deploy to justify tearing down statues of Jefferson and Washington. And if the Royal Governor of Virginia didn't arm slaves, would you be of the opinion that the Declaration of Independence would never have been written?
Of course, the British Empire didn't outlaw slavery for several decades after American independence. So, were the British planning to abolish slavery in America before the Battle of Lexington? Or were British officials merely engaging in expediency much as Lincoln would do several decades later? After all, the British government did employ foreign mercenaries to suppress the rebellion.
And then there is this bit from Wikipedia on the subject (original sources footnoted there):
As a response to the fear that armed blacks might pose, in December 1775, Washington wrote a letter to Colonel Henry Lee III stating that success in the war would come to whatever side could arm the blacks the fastest.[16] Washington issued orders to the recruiters to reenlist the free blacks who had already served in the army; he worried that some of these soldiers might cross over to the British side.
Ironically, Colonel Lee is of course the father of Marse Robert--the Confederacy's most famed general. But it can be seen that Patriot leaders recognized that they needed to recruit black manpower--which gets us back to Robert E. Lee and another case of irony. In the waning days of the American Civil War, Lee successfully got the CSA government to allow the recruitment of slaves, a proposal that earlier stunted the career of Patrick Cleburne.