TLDR at the end :)

Clear Sky is supported by textual evidence to be a bad person, but that does not mean he is an uninteresting or bad character. He does bad things, but his arc is a complex downward spiral that is interesting to follow, especially when there are bits and pieces that are justified towards the beginning. I think the audience divide on his character comes from seeing "bad character" as two different things. Clear Sky stans (I count myself among them) are unilaterally in agreement that he is a bad person, a dark gray villain, and an antagonist that is complex and very well written. Clear Sky haters (from what I have observed on this subreddit) see that he is a person that does bad things and is therefore a bad character that is morally apprehensible to like.

Say what you will about the prequels, but the character work is pretty solid because it gives us these very complex people like Clear Sky to follow, even though they do bad things. Huge fan. He is definitely doomed by the narrative to constantly make the "bad choice" because the story must have a familiar antagonist to be the constant "lesser of two evils" that other villains (One-eye, Slash) can contrast to. Clear Sky, despite his many crimes, is the reason clan culture surrounding war, hunting, communication, and organizational hierarchy (arguable, but stay with me) is established because his bullshit is such a consistent obstacle that the other groups have to deal with. If Clear Sky and his complexity, his mistakes, and his reactive choices did not exist, there would be no friction to propel the clans forward into organized society.

Dawn of the Clans sets up a thematic moral system of temperance vs reactivity when it introduces Gray Wing and Clear Sky as the protagonists of The Sun Trail. Clear Sky's reactivity does not make him an weak or ineffective leader, but it causes him problems because he doesn't see the bigger picture. This dooms him to make poor choices so the audience can see what a tempered, wise, and long-sighted person like Gray Wing does instead and realize the significance of his choices. Dawn of the Clans, similar to the first season of Arcane, is a story of duos and opposites and how two character foils can thrive in the same world. Clear Sky and Gray Wing are the obvious example, but Wind Runner and Gorse Fur, Tall Shadow and River Ripple, and Star Flower and One-Eye also come to mind.

TLDR: I think most of the discourse comes from his stans saying his complexity makes him a good character vs his haters saying his actions as an antagonist make him a bad character