Why Oh Why

Well we managed to get 21 fish out of the nets. We've stopped multiple times and were attacked almost every time we stopped.
 
It feels like we are making progress across the Dark Lake.
 
Some dark dwarves attacked us. Zeder tried to calm and bargain with them. As I was trying to stealth, the barb decides to attack them. Turns out they were miners and just looking to make some coin. Why oh why did my party decide to attack without even trying to make a bargain with them?