To a child, the Founding Fathers were heroes through and through who didn't tell lies and flew kites during thunderstorms.
To a petulant child, the Founding Fathers were corrupted white men who owned slaves, had wealth, and wrote documents that favored their cause. Except for John Adams who was a "community organizer" just like Barack Obama (that bit of wisdom was uttered by the brilliant actress Laura Linney who played Abigail Adams in the TV miniseries, therefore qualifying her to speak in an inane manner and be taken seriously).
To an adult, the Founding Fathers were men, neither perfect nor heroic, who in the face of unprecedented events carved out a society that was, and is, unique in the annals of world history.
History will always be looked at through the filter of current events. That filter may help the observer understand facts, but it does not change facts. To many on the Left, the Founding Fathers were evil men who owned slaves and who were so callous as to count slaves "and other persons" (generally Native Americans) as only 3/5 of a person.
This is a simple way to make the case that the Founding Fathers were evil, just like the snotty teenager who makes the case that Dad is evil because he makes you bring the minivan home by ten. But if you take the time to understand the Federal Compromise, as the 3/5 compromise is actually known, you will see that it shortened the route to abolishing slavery for the entire country.
If counted completely, free citizens, slaves and Native Americans in the South would have far outnumbered the population of the North, thereby giving the South nearly complete control over the Presidency and Congress. As abhorrent as it sounds, by counting the non-free population in the manner they did, the power of the South was limited, the Union was strengthened and ultimately, seventy years later the horrendous practice of slavery was abolished. It should be noted that slavery was relied upon by European (and hence New World) powers for 300+ years. To take that institution down in 70 years is pretty good.
So the next time you're in an argument with a petulant Leftist who hates the rich white men who founded this country, hit them back (nicely) with some facts.
Happy Independence Day.