I challenged a fine (one and only ever) from AMET and I won. It was a 1200 pesos fine, and 8 page sentence in my favor.
I guess one's willingness to challenge (anything) depends on one's ability to know the local laws, have a gift of "thinking and analyzing like a lawyer" and an excellent fluency in Spanish both written and oral, and not just street Spanish but legal spanish.
I guess it depends upon each person's personality, spirit, and how comfortable one feels chellenging to stand one's rights.
And truth be said, many Dominicans actually respect and admire you for standing your ground because many of them can't or don't want. And they admire you for that.