Abusing might not be the right word but you are taking advantage of the unethical system because you know it requires persistent devaluation of the money. But you bring up a fair point. By borrowing fiat you are contributing to the expansion of the money supply which could potentially harm others. This monetary supply expansion will happen with or without your involvement and your involvement is a mere blip but I think philosophically it is a reasonable question. I guess it comes down to if you think the positives outweigh the negatives.