“Do you think that airline corporate interests play no role in decisions to charge under this statute?”
When there is a crime, and there is a viable suspect, charges will be filed and an indictment sought.
In this case, it would appear, that there was not evidence or a crime and prosecutors did not believe they could get an indictment.
Had Dao been indicted and convicted, the check United wrote to Dr. Dao would have been much smaller.
In this case, people would not change their minds based on whether criminal charges were filed - they would feel it was an additional injustice done to Dao by United. There would be protests outside the courthouse.