I’m rereading Harry Potter and the Philosopher’s Stone and it kinda hit me, the Centaurs knew that Harry would die. Firenze saves Harry and all the others get angry, saying they are not to set themselves against the heavens and points out “have we not read what is to come in the movements of the planets”. Firenze tells Harry before he leaves that he hopes they have read the planets wrong. Firenze, Bane and Ronan knew Harry Potter would die in that forest by the hand of Voldemort, only not when. So when Harry shows up in the forest and is nearly killed by Quirell and Voldemort that inhabits his body, Bane and Ronan believed this is what the planets meant. Firenze saving him goes against that. They were not angry he helped Harry but because they believe Firenze interfered what was foretold. Even Firenze refuses to tell Harry why they are angry, because he can’t bring himself to tell an 11 year old “you are supposed to die in here”. Of course, what no one knows is that the centaurs will be right. Harry will die in there by the hand of Voldemort, only that it will happen 6 years later.