A ) No one hates Stannis, Stannis is awesome
B )They weren't about to negotiate peace, Jon wasn't there to negotiate, but to kill Mance, and in reality all Mance did was demand the Night's Watch surrender or die.
C ) The fight was extremely lacking, since apparently most of the budget went to episode 9, but we can assume that they didn't expect to be attacked north of the Wall, so Stannis' men caught them unawares.
D ) He was outside his kingdom by a couple hundred yards and saved his kingdom from a wildling attack (which no one else was willing to do). Unless of course you meant that he's not really the king, then you'll face the wrath of every Stannis-fan on the forums shortly...