To err is human; and it is wrong to condemn people based on the standards of another era.
Why would it be inappropriate in any era to criticize hypocrisy? If Jefferson's claimed principles did not match up with his observed actions, that's hypocrisy whether it happened in 1785 or 1985, especially when it concerns a crime as serious as chattel slavery or rape. And you know what? Those things were no less controversial in 1785, anyway. We know that "people" knew that these things were wrong, because they wrote about them. Voluminously. Entire nations had revolutions over the concept of universal human liberty, including his own. Jefferson himself both admitted fault later in life, and was openly critized by family and colleagues throughout his
entire life.
To your other point, Jefferson could indeed have released his slaves, and indeed for a short period of time they
were free and initially declared their intent to stay that way, during a trip to Paris (where slavery was already illegal, more evidence btw that your claims of his naive innocence are nonsense). But their situation was not such that they could agree to manumission without severe risk to themselves, at that point in time, and Jefferson was able to persuade them with promises of "extraordinary privilege" and the manumission of his children when they came of age to "voluntarily" return to the US and back into his service, including his sixteen year old sex slave and the first two children he'd had with her.
Things
were a lot more messy than a simple black-and-white morality will help you resolve. But stamping your foot and refusing to condemn or even critique the behavior of anyone in antiquity is not pushing the conversation forward any more than unreasoned critique would.
I would also observe that the only living parties who could be affected by this conversation in any way are the Jefferson/Hemings descendants, and in a more abstract way all citizens whose rights are considered contingent on status in the present. Jefferson himself is dead. Long ago, and his feelings cannot now be hurt by an analysis of his decisions in life. Discussing morality in the past is discussing morality in the present. It is asking: what happened, and what can we learn from it? Ideally, it is asking: How can we do better? There is no cost to "attacking" the reputation of a person long dead. But refusing to do so is hagiography, not history, and that
can be quite dangerous, because it prevents serious conversations about the past and future of the nation. If the teaching of history is to be of any value for the young, then we need to populate our history books with humans, not saints
or demons.