probably don't have a great understanding of the context of what he did and how he fundamentally changed the US for good and bad. Not to mention his motivations and the consequences that followed.
As I said, his image is that of "the guy who freed the slaves and paid for it with his life". There's so much more to know about him than that though.
People overlook the bad he did because he righted a huge wrong in American society. He should get credit for the good he did, but he shouldn't be excused for the bad. I'm not saying he is the "worst", maybe not even in the "bottom" 5, but he did terrible things for our country.
I often think of FDR as being the worst. He sucked.