Andrew:
As a father I try to teach my children to respect nature and life in general. We spend a lot of time outdoors and we practice the "Leave No Trace" concepts taught by the Boy Scouts. Basically, if they find something special, even a rock, I encourage them to leave things as they found them so the next person that comes through can have that same experience.
That said, I would not hesitate or give a second thought to killing anything that could possibly harm my family. I would try my best to avoid it, and have done that so far, but I long ago made up my mind as to how I would handle a real threat.
Don't come down too hard on your Dad. I'm sure he's trying to do the best he can with what he has. I know I didn't make it easy for my father and my children are returning the favor ten fold.
JohnNJ