I think the red cunt wants to devour him, but Stannis seems to hold some regard Jon Snow being Ned Stark's son.
I feel that Jon Snow sold Stannis offer extremely short to Mance, Stannis told him he'll let the Wildlings have lands and settle south of the wall! the whole reason they fought and were to continue fighting if they had defeated the night's watch and got passed the wall! Basically they were gonna do everything they were set out to do with the addition of being legal residents/neutralized citizens of Westeros, which means they would avoid future wars with the kingdoms which were to surely crush them at one point or another, Jon Snow didn't tell Mance the full offer and didn't argue any of these points, felt like they were just pushing for Mance to die.