Why such a bad rep with hatchery fish?

I do not know why hatchery fish are so hated.

Is it because of the genetics?

I am assuming hatchery fish are not derived from native stocks and "outside genes" are where the stocks come from.

If they used native stocks to fill the hatchery pens would that be acceptable?

Is using native stocks to fill hatchery pens not good enough for the purist?

If native fish are so low in "natural" conditions would it not be beneficial to use native stocks to fill hatchery pens be beneficial to helping natural stocks recover ?

I know I may be uninformed but this is why I am making this post.