Eren spent years of his life looking for an alternative to war with Marley and all his efforts in attempting to do so went out the window the instant Marley themselves declared war on Paradis, fully intending on slaughtering all of them in order to take what they want for themselves and much like those living and Shiganshina that faithful day in the beginning the civilians of Marley and people like Gabi will only see Eren as a pure devil nature.