I think the reason behind Rumple’s wrath towards Milah and Hook was more about Bae than it was about him. He was hurt and angry because she left her son for another man – a pirate- which leds him to become a person who seeks for power and controlled by his hunger for power, he became his worst fear his father who also left his son because of his selfish needs. Eventually Rumple made the same mistake which haunts him for forever. The guilt was unbearable and he knows Milah was also responsible from Bae’s lost. And the wrath and hate he held for her became more and more powerful each day not only because Milah was responsible too but blaming her made it easier to endure the anger and hate he felt towards himself. And Milah who has no love or responsibility towards her son deserves that much hate and anger