This is kind of vague, however, my best answer is the human rights issues here can relate to 1) Candy being forced to kill his dog 2) whether it is right or not to kill Lenny due to his innocent "accidents"
1) Candy is faced with human rights issues because he is pressured in killing his old dog despite repeating numerous times that he did not want to/he shouldn't so they killed it for him
2) Whether or not it was right to kill Lenny brings up the concept that yes, Lenny was dangerous to himself and everyone else but recklessly innocent, so does that make it right for them to kill him?
This is open to your opinion, but I think this might help.