He was offered one chance to accept the legitimacy of the southern rebellion. That was the primary purpose of the so-called commissioners. Everything else was secondary. An end to the rebellion was not on the table, so far as the Davis regime was concerned, so there was nothing to talk about. Had the discussions been open to all possibilities, and had Lincoln spurned that chance, then you would have an argument. But expecting Lincoln to surrender, and then criticize him when he did not, is nonsense.