I'm not even sure that Ellie does anything negative from the leaks, though it's rumoured (IIRC) that the epilogue is her going on a revenge trip against the opinion of her partner and I assume the change of character perspective would entail seeing Ellie under a different light.
Putting aside the people mad at the SJWs

it seems the common complaints are :
- People mad at Joel getting killed or not playing Ellie for the full game and generally a strong kneejerk at the idea of being forced into the role of their tormentor.
- Fears of hacky writing looking for shock value at all cost and devolving into "misery porn".
- Anger at gay character they're attached to being brutalized (maybe killed) and the possibility it plays into tropes ("Bury your gays" and all that.