If you want to write him off that quickly, feel free, but you're short sighting yourself. Finding oneself in a society with slavery, Jefferson purchased slaves from owners that abused them, and then did his best to ensure others knew the cruelty of those individuals, triggering a local society shunning of them and repercussions in their church - which at the time was very powerful. Jefferson's own handling and treatment of his slaves was extremely humane considering the status quo at that time.