I think the slope of the stick force per G is positive. It's just not linear in the regime they are concerned with.
Why do you think that? I hear a lot of people speculating that's the case, but no one has has definitively proven that one way or the other, directly from any data so far publicly available.
Boeing's statement is basically MCAS is an augmentation to maintain proper stick force, but as far as I remember, reading everything here and everywhere else, they very carefully never say where they start from.
Someone fly the plane w/o MCAS and report back. Then I'll believe it.