Can I guess?Just a guess–nobody “kill” me,please.:)
1.Kayin was punished for killing Hevel–not because he defied specific instructions not to–but because it was a given:WRONG.BAD.
2.A Jew has 3 traits ingrained in his very being.We are bayshonim,rachmonim,and gomlei chasodim.A murderer is doing away with all mercy,and that resistance takes conscious thinking.