Violent races in space?
The idea that space faring races could be violent seems unlikely to me, because such races would likely destroy themselves, materially, before mastering space travel, which we know is incredibly difficult.
It requires elevated brain power and creative brilliance to make the jump to faster than light travel required for effective space travel.
Violence in a race makes this level of mental brilliance highly unlikely, if at all possible.
Co-operation is also a key feature of a space program which requires trust and good intentions among participants. This would be unlikely among a warrior race.