At any given time, any person and any company could be easily convicted of enough serious crimes to put them in prison for life or out of business. Prosecutors don't pick cases; they pick defendants, based on what are hopefully well-intended criteria. They then go through the extensive but essentially mechanical process of the justice system, which hopefully at least serves to shine enough daylight on the matter that prosecutor misbehavior is hard to hide.
Saying we should not pressure them to pick in a way we would prefer is to abandon the only actual influence over the system we have.
Otherwise you'd more often run into situations where you couldn't prosecute someone because a statute didn't spell out their exact actions even though in spirit they had violated it.
Getting a DA fired solves nothing. What happens once you have achieved it? What have you accomplished? The law remains the same, and these type of cases continue to be brought.
Change is difficult. But I hope that if people really cared about this they would put as much effort as they can into changing the law, rather than trying to place the blame on a single individual - because the latter can easily result in even more misunderstandings.