We're dancing around the point here.
Point being, that we cannot always determine the effects of continuously repeating small, seemingly benign actions. Taking tens of thousands of tons of salt from one place on Earth and dumping it on another where salt is relatively scarce has unknown side effects.
Hand-waving over it with "eh, but it probably won't hurt anything" misses the point of the discussion. That is the attitude that tends to get us trouble.
Smoking: "eh, that's probably not what's causing you to get sick"
Climate change: "eh, it's probably not us"
etc.