Earlier quoted context omitted.
Your friend was treating a return policy as a rental policy. I don't think that's in the spirit of a return policy.
Are we going to blame people for not buying WinRaR licenses next? These are businesses, they offer the policy for a variety of reasons, I am free to use them within the terms; it sounds a bit out there to categorise returning a product in a “no questions asked return” policy as unethical unless I actively sabotaged the product or did anything other than use it and give it back.
It's not illegal to use the agreement in this way, and I would never try to make it so. But I would absolutely look down on someone for behaving this way.