As a Republican annoyed by MichelleBachmann's claim that the Founding Fathers worked tirelessly to end slavery?

.....I nevertheless wondered: Considering that a few of the Founding Father's certainly DID work hard against slavery -- I'm thinking first of George Mason and Alexander Hamilton, for example -- how many of the Founding Fathers needed to be active Abolitionists for Bachmann's statement to be accepted as an appropriate summarization?