I wasn't justifying anything.
The point I am repeatedly making here is that it's the consequences that make an act unethical, not the act itself, by itself.
It's really not that difficult to separate the act and it's consequences.
Extreme example: putting a knife in someone's heart per se is not unethical; it's the fact that someone dies as a consequence that makes it unethical. If all it did was tickle and make you laugh a bit and absolutely nothing else, then you'd find it very hard to explain why it's unethical, wouldn't you? It seems counter-intuitive, but if you're intelligent you can get past that.
That in mind, let's try this again: Both me and a store happily agree that I will buy and then return an instrument under their returns policy. I return it in MINT condition as promised, and the store gives my money back as promised. They are happy, I am happy, and there are no negative consequences to anyone, ever.
If there were negative consequences - as I plainly agreed there can be in previous posts - the act would be unethical. But in my hypothetical, there are no negative consequences.
And the final point is this: there is nothing inherently unethical about purchasing a bass and then returning it. It only becomes unethical when there are negative consequences.
So you can't just pronounce an action 'unethical' without regard to it's actual, real life consequences, and you can't just assume that the consequences - if any - will always be negative.
Got it?
Now that that's cleared up, you should all know that I personally do not condone doing this. It would have been easy for me to do when I was in LA, and it was an option offered to me by staff at one store (which is the inspiration for my hypothetical). I knew, however, that a) the policy wasn't there for this kind of thing, and b) I would still be financially better off hiring from elsewhere. Also, I would have had the bass for two weeks, playing frequently and travelling often, increasing the likelihood of this bass not returning in mint condition. So I didn't risk those consequences or the personal guilt associated with abusing the trust of the store. I still disagree that there is a clear-cut, black and white answer on the ethics of this, because situations and circumstances are different every time. In my case, it could have been very unethical for me to do it. In another person's case, there might have been no negative consequences for anyone involved. I still stand by the statement that there is nothing inherently unethical about purchasing a bass and then returning it, and it only becomes unethical when there are negative consequences. And no this is not "getting away with it" - because there's nothing bad to "get away with".