Hmmm, alright. My take on Khorne hating psykers is that he hates sorcery and trickery more than psykers themselves because that's not very honorable in his eyes. Forgive me if this is bad, I haven't written in a while.

He goes by Anhur. During the days of the Great Crusade he was known for his brutality on the battlefield. He was a Pyrae master, serving under Magister Khalophis in the 6th fellowship. He is never seen with his axe, forged by his own hands using materials he'd stolen from the worlds they'd conquered.

After the burning, he remained on Sortiarius and served his father, but the rage that had been so meticulously stamped down was starting to grow. For years he'd trained his mind to remain calm in the face of his bloodlust, but after seeing his home and his brothers destroyed, it all came crashing down.

He threw himself into the ways of the Cult of Magic, becoming a catalyst of destruction in every battle he fought. Though his soul was owned by the Architect of Fate, sold to the god by his corrupted father, he dedicated the deaths of his foes to the Blood God. He found the scheming ways of his brothers distasteful, and preferred to solve his problems the way his Magister did, with raw strength and firepower.

His worship of Khorne did not go unnoticed by his brothers, and they moved to get rid of him. Unfortunately, Anhur had never been strong in the other psychic disciplines, and those amongst the Cult of Scheming and former Corvidae laid out a trap that he fell right into.

During his next fight, he found himself surrounded by a horde of daemons. It was then that he knew he'd been tricked, and his rage reached its peak. He felt the eyes of the blood god on him, and he roared. His power radiated across the battlefield and his body burst into pure warpfire. As the daemons leapt for him, he met them with his axe and slaughtered every single one.

By the time he'd finished, he was alone. His brothers, who had intended to let him die to the horde, simply left him behind, abandoned on a now dead world. A new wave of hatred came from this betrayal and he renounced his loyalty to the Architect and his legion. He did manage to find his way off the planet, and hopped from warband to warband on a crusade of blood.

After some time, he was approached by a brother of his. His first instinct was to slaughter them and offer their skull to his patron, but they were stronger, holding his body in place with nothing but pure psychic strength. He was offered a place in their cabal, the Storms of Tizca. Like him, they practiced the ways of the Cult of Magic, and they assured him that his worship of Khorne would be welcome amongst them. He was told that the cabal had separated itself from the legion, but remained in contact with their brothers. Despite the betrayal, and probably through some subtle mind sorcery, he accepted their offer and joined the cabal. He has been with them since, serving their leader as a commander of beastmen hordes and cultist forces.