Sure we can. Some 19th century people made a decision to support slavery and others did not. The Free Soilers who fought for the Union deserve special credit for both being way ahead of their time and for putting their lives on the line for the liberty of all Americans.
[You] Sure we can.
"We"? What, are you God? Are all those people on the other thread participating in Spurgeon's devotionals addressing the wrong Person?
Or do you just want a pretext for holding political show trials of dead men? Sounds like an Old Left front-politics enthusiasm to me. Always wanting to put someone on trial. Now they want to arrest Dubya.
It is too easy to sit back in our warm, comfortable, politically correct world today and pass judgment on men far better than ourselves. Before passing any judgment, you should carefully consider all the circumstances of the situation. In addition, you should know than many of the free soilers held their beliefs to live free of blacks.