The Founding Father of modern Conservatism called the British hypocrites about slavery

In his speech on Conciliation with America, Edmund Burke said the following to the House of Commons:

Slaves as these unfortunate black people are, and dull as all men are from slavery, must they not a little suspect the offer of freedom from that very nation which has sold them to their present masters?--from that nation, one of whose causes of quarrel with those masters is their refusal to deal any more in that inhuman traffic? An offer of freedom from England would come rather oddly, shipped to them in an African vessel which is refused an entry into the ports of Virginia or Carolina with a cargo of three hundred Angola negroes.

Now, there may be some issue raised as to if Burke really is the Founder of modern Conservatism, that's a title given to him by (I think) Kirk and repeated by many, many others. If that's the primary response to this, you missed the forest and the trees. Keep in mind, Burke isn't just stating that Britain brought them across the sea. Burke is also stating another crucial fact - The future Americans (then British subjects) were fighting back and trying their best to prevent future shipments. What does Burke mean when he talks about "refused an entry into the ports of Virginia or Carolina"?

According to some estimates, less than 300,000 slaves were brought to America after Independence was declared. More than double that were brought here per the wishes of Parliament and/or the King. That represents some roughly 5% total of human traffic. As horrible as this is, let's understand the full scope of what was done.

According to the same estimates with less numbers omitted, Britain shipped out over 3 million souls from Africa. What percentage is that? These estimates state that in total roughly 12 million were trafficked including what was done by Portugal, Spain, France, and others. Over 3 million is at least 25%.

Is Edmund Burke correct on his call of hypocrisy? If so, then the question is this: Is slavery really America's original sin? At 25%, is it more correct to say that slavery Britain's original sin?

Why should America get the blame when our forefathers repeatedly and desperately tried to tell the King "NO"?