Musar for Bava Kamma 48:13

(Ibid. 17): "For I heard them [the brothers] saying: 'Let us go to Dothan [nelchah dotainah],' which Rashi interprets: 'to seek against you nichlei datoth [legal devices (suggested by 'nelchah dothainah')] to kill you with." The explanation: It was decided by them that Joseph was a man of lashon hara, who provoked their father to hate them. And who knows how much contention he would stir up among them? They, therefore, sought some pretext to rid themselves of him in a way which would not make them "murderers" legally. As far as his being killed indirectly through them, this did not concern them. And as to their saying (Ibid. 60): "Let us go and kill him," this was meant in the same indirect sense. As stated in the well known Gemara, Makkoth 23a): "If one speaks lashon hara, he is fit to be cast to the dogs, it being written (Shemoth 23:1): 'You shall not bear a false report,' preceded by (Ibid. 22:39): 'To the dog shall you cast it.'" And we find in the Gemara (Bava Kamma 24b): "If one sicked a dog against someone, he is not guilty [of murder]." And even though by the law of Heaven, he is certainly liable for "indirection," too, they thought that in this instance they would not be liable by the law of Heaven because Joseph was a man of lashon hara and contention.