What if it was a moose? Who do you sue, the DNR? The Queen? Why not accept it and get on with life, instead of always looking for someone to blame.
To me, while I know this guy is within his legal rights, I think it reflects poorly on his character. I'm not claiming the dog owner is innocent, I'm just suggesting that if people were a little more reasonable, the world would be a better place.
(There actually was a case in Italy where a driver sued the parents of a deceased bicyclist for damages done to his car when he hit the guy. Furthermore, I thought all of us self righteous types were of the opinion that parents are responsible for their children, so what's the diff?)