I don't think it is just the authors of the US Declaration of Independence who were unsavoury, but also some of the things in the text itself. The most well-known aspect of its unpleasantness is the part about "merciless Indian Savages"; less well-known is its opposition to cultural rights for French Canadians ("For abolishing the free System of English Laws in a neighbouring Province...")

When Britain conquered New France, Britain promised that French Canadians would retain cultural rights, including the freedom to practice the Catholic religion, protection of the French language, and the continued use of aspects of French civil law in the legal system. It is that last aspect of Britain's commitment which the authors of the US Declaration of Independence found so offensive.

(Strangely, when the US agreed to buy Louisiana from France 27 years later, the American objection to the French legal system appeared to have vanished, and Louisiana still partially uses French civil law to this day.)