Right... as it stands, the Bundschuh only dislike Corsairs because their friends hate them. The Unioners can still make deals with Corsairs.
Just because friends of their friends are at war with the Corsairs, doesn't make them enemies. Hell, they could get on well with Bundschuh, but still receive supplies or trade from the Corsairs.
Shades of grey, shades of grey. Being allied to the Outcasts does not make one an Outcast oneself.