I'm re-reading ACOK, at the beginning when Stannis is discussing with Maester Cressen about how the Stormlords won't join his cause. They talk about his two potential allies - Renly and Robb, I understand his objections to joining with Renly - I believe he is correct in this matter though I wish they'd have more sense and worked together, but I can't understand why he rejected the advice of Cressen to side with Robb. Stannis calls him a green boy and claims he will not give up half of his kingdom (Funny because he hasn't won anything yet) and then rants about how Robert treated Ned as a brother and not him. Now I believe it was foolish of him to not try and form an alliance with Robb, it would have suited both parties so much- Stannis would get loyal men he needed to remove the Lannisters and Robb/Cat would gain a proven battle commander and a man more than capable of dealing with Frey's and Boltons to aid them in their quest for justice.
Would I be correct in saying that Stannis pride particularly in relation to his relationship with Robert is the cause of this naivety?