You can't complain about an "argument by definitions" when your entire argument rests on applying a label like "book banning" that has significant cultural weight. Book banning sounds bad, it sounds authoritarian, and that is basically your entire argument. So yes in that scenario it is pretty fatal to your argument if you are completely misapplying it to a situation that cannot actually be described as involving book banning at all (because no books have, in fact, been banned).