Killing a human being as a sin atonement to Hashem is completely against Torah.
Although I too am not a theologian, I am still confident enough to state that I believe if examined by anyone, the prohibition in the Torah against human sacrifice does not apply to the Sacrifice of Jesus. This is because, I believe, in the Torah, the prohibition is to prohibit the common activity of pagans at the time who sacrificed human beings forcefully, against their will, to gain favor with their gods.
This is not the case with the One Sacrifice of Calvary. That Sacrifice was willingly accepted by the Son as His Father's Holy Will. Indeed, while He prayed “this cup pass over me” He also prayed “not my will but your will be done”. It was His choice to Sacrifice Himself for everyone else. This is significantly different than the pagan practice of the day. Thus, it is not against Torah. In fact, I would argue it is in compliance with Torah.
I believe you said upthread in another post something to the effect that the entire Torah is summed up in the Golden Rule. Jesus Himself said this as well, but also when asked the same question 2000 years ago, in addition to restating the Golden Rule you quoted He also said the entire Law is first to “love God with all your heart and understanding”, then “love your neighbor as yourself” (a positive restatement of the Golden Rule you quoted).
Thus Jesus obeyed Torah to the end, not only “loving (His) neighbor as Himself” (by sacrificing himself for others’ sake) but also by “loving God (the Father) with all His heart” (by complying with His Holy Will that He lay down His life for all men).
No; rather than being contrary to Torah, His Sacrifice was in perfect obedience to it.
So; this means a NON-human has to die to take away sin?