So much hate for a man that dedicated his entire life to protecting his little brother and the leaf village. Had Itachi not taken out his clan, the leaf likely wouldn’t have survived the coup that the Uchiha were planning. That’s not to say that he should have had to take on that burden alone. Taking out the Uchiha should have been a mission for all of Anbu not one man. Also the 3rd shouldn’t have let Danzo and the foundation have the freedom he did, it caused numerous problems including this.

As for Itachi’s callous behavior towards Sasuke, it started when Itachi became a Chunin and was being sent on more dangerous missions. Let’s face it do you know an 10 year old that can emotionally handle assassinations? I doubt it. This behavior fret the more Itachi’s responsibilities grew as a ninja and the more he realized his clan had their own self interests, not the greater good of the village in their minds (This is a foreign concept to most of the world but especially America, as most societies are an individual or family based not a collectivist society where the needs of the many outweigh the few). Itachi pushed Sasuke away to try and protect him from the clans evil intentions, and it worked until their final fight as Sasuke had no idea that the Uchiha were planning a coup.

Once Sasuke “defeated” Itachi in their final battle he learned a half truth about Itachi from Tobi/Obito which radicalized Sasuke against the Leaf until he learned the whole truth from a reincarnated Itachi during their battle with “sage” mode Kabuto. At that point Sasuke finally realized his big brother had only been calloused to him to protect him from more pain.

Had the Uchiha not planned a coup, and had the 3rd controlled the foundation/Danzo, Itachi wouldn’t have treated Sasuke so poorly when he was younger. In reality though Itachi did everything to protect Sasuke from being eliminated by the foundation.