“. . . its decision would leave fliers with ‘very limited legal redress’” for abuse, . . .” So true.
And now that TSA agents know that, we can expect the abuse to get worse. It’s a great position to be in; mistreat whomever you don’t like and call a real cop if things don’t go your way. It’s an invitation for more of the same.
And they are expanding beyond the airports.

While prosecutors have discretion, discretion, like any other government action, has to have a rational basis. Letting cops get away with these things because they are police officers, calls into question ALL prosecutions of these types of offenses.

Additionally, victimization isn’t less of a victimization simply because someone with a badge does it. In some ways, it is worse. Victims have no right of self-defense (unlike in other cases) and can even suffer additional victimization if they complain.