Good for him. I wouldn't have met with them either. What they wanted was to negotiate with Lincoln the permanent split of our country, and to condemn blacks to untold decades of slavery and bondage. That is not "peace."
It's not war - slavery ended peacefully in numerous other countries without waging war. In two countries even after Lincoln's war. And if the intent of the union was to abolish slavery, why didn't the United Stated invade other countries to end the practice, and why hasn't it invaded countries which practice slavery now?
If the preceding was justification for ending slavery, would that have justified England invading the US to end it before the war?