Also, if we must judge by the morality of the times, we must also view abolishing the nobility and separating church from state to be immoral and unchristian. You seem to want to avoid a "modern moral framework" when it would tarnish the reputation of a founding father, but embrace it otherwise. You're not advocating slavery, but you don't want to judge slaveowners harshly.
It's perfectly fine to acknowledge the good that people do, while also acknowledging the evil. Jefferson, Franklin, and Washington all held slaves, and they were all evil for doing so. If we judged past people by our modern standards, they would all be condemned, and if we believe at all in some form of moral progress (which you must, since you bring up American freedom and the establishment of a secular republic as virtues) then we can condemn them all for some things.
I've lived long enough to see a distinct shift in what people consider moral and immoral. Are you certain in your moral rectitude? (I am, even though I fall short of it, and change my mind now and then.)
> these men were judged by the morality of their times
Half the colonies considered slavery to be moral in their time. So much so that, a few years later, fought and died in a terrible war to defend it.