One of the favored propaganda devices that they use is that of Samuel Johnson, a well known British author at the time. Johnson examined some of what he heard coming from the Continental Congress and among other observations, asked this question:
We are told, that the subjection of Americans may tend to the diminution of our own liberties; an event, which none but very perspicacious politicians are able to foresee. If slavery be thus fatally contagious, how is it that we hear the loudest yelps for liberty among the drivers of negroes?
Just a month ago I wrote this about one of Burke's speeches, where he notes the hypocrisy of the British (of all people) offering freedom to slaves, after they were the ones who did all of the colonial shipping across the Atlantic! But anyways, in the same speech Burke gives what is actually a very concise answer to Johnson's query. Burke said:
There is, however, a circumstance attending these Colonies, which, in my opinion, fully counterbalances this difference, and makes the spirit of liberty still more high and haughty than in those to the northward. It is that in Virginia and the Carolinas they have a vast multitude of slaves. Where this is the case in any part of the world, those who are free are by far the most proud and jealous of their freedom. Freedom is to them not only an enjoyment, but a kind of rank and privilege. Not seeing there that freedom, as in countries where it is a common blessing, and as broad and general as the air, may be united with much abject toil, with great misery, with all the exterior of servitude, liberty looks, among them, like something that is more noble and liberal. I do not mean, sir, to command the superior morality of this sentiment, which has at least as much pride as virtue in it; but I can not alter the nature of man. The fact is so; and these people of the southern Colonies are much more strongly, and with a higher and more stubborn spirit, attached to liberty than those to the northward. Such were all the ancient commonwealths; such were our Gothic ancestors; such, in our days, were the Poles, and such will be all masters of slaves, who are not slaves themselves. In such a people the haughtiness of domination combines with the spirit of freedom, fortifies it, and renders it invincible.
Note that both Samuel Johnson and Burke are observing how the spirit of Liberty appears to be more vivid in southern colonies. Now of course Burke wasn't addressing Johnson at this time. However, it does render the question Johnson asked relatively useless.
What Johnson is responding to(without wording it that way) is their heightened sense of jealousy over their individual Liberty. Patrick Henry is very well known for using that specific word. "Guard with jealous attention the public liberty. Suspect everyone who approaches that jewel." Jefferson also uses that word in the Kentucky Resolutions. "Free government is founded in jealousy, and not in confidence; it is jealousy, and not confidence, which prescribes limited constitutions to bind down those whom we are obliged to trust with power; that our Constitution has accordingly fixed the limits to which, and no farther, our confidence may go."