Fantastic 4 Silver Surfer Sequel

I thought the Silver Surfer was a hero not a bad guy. Why in the Fantastic 4 Sequel hes bad?

When he first became the Silver Surfer, he only followed the orders of Galactus–without question. After coming to Earth, he learned that the people of Earth cared about what happened to their planet, he openly defied Galactus and defended them.

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