Question

When reading the medieval authorities (Rishonim) on the Torah portion, one gets the sense that they were uncomfortable with the privilege given to the avenger of blood to kill.
So much so that some maintain that his permission applies only after the killer’s sentence has been determined in a religious court.
However, the Ketzot brings that Rashi and Maimonides hold that the avenger of blood is permitted to kill in any case.
But how? Murder is forbidden, isn’t it? Seemingly even for a murderer.
I thought of a possible direction: that in fact it is forbidden for the avenger of blood to kill, but the avenger of blood is acting unintentionally. That is the meaning of “his heart grows hot.” In other words, he is not in control of himself and therefore is considered unintentional.
One could discuss whether it makes sense to say something is permitted or forbidden in a situation of deliberate action, which relates to a person making a decision and therefore being subject to command.
From someone acting unintentionally, you can ask for atonement after the fact, but to command him or discuss the prohibition of his committing a transgression — that is outside his conceptual world. What is the point of commanding someone not to do something if he is doing it unintentionally?!
And assuming the avenger of blood is in such a psychological state that he is considered unintentional — that he does not control or choose his actions because “his heart grows hot” — then the question of whether he is permitted to kill or not does not really apply. (Maybe after the fact he would still require atonement.)
(It reminds me of how the law treats premeditated murder differently from other, more lenient degrees.)
The Torah is describing a situation — it’s a given! He is going to kill! And from there the Torah builds a defensive system of the city of refuge, etc.
What does the Rabbi think of this direction?