You might want to go back and read the BPGD entry for Diqiu again. http://www.eyrie-productions.com/Forum-docs/DCForumID25/267.html The section on the Water Tribes explains that there is a long standing animosity between the two tribes. The Northern tribe might not be jerks in general, but would be more likely to let that side of their personality out when dealing with someone from the Southern tribe.