Forget about ethics for a while. Who should have ownership versus who does have the ownership differs. The protocol listens to the latter. And since ownership is defined by the protocol, whoever has the keys is the owner.
It's almost as if Bitcoin is designed to be electronic cash 
Old fashioned paper banknotes are exactly the same: you may have found it, and you may not be the owner based on ethics, but when you spend it, none of that matters to the receiver.I was stuck on: technically, you can spend the coins when you've got the keys, and technically, you can drive the car when you have its keys.
It's just that in the former, the protocol sees you as the owner, while in the latter case, the protocol (in this case probably just the legal system, right?) doesn't - no matter how many miles you put on that car.
Is there any legal equivalent about BTC?
Do we want legalities/regulation?
I think KYC would be nice if it was optional, not mandatory.
I don't know how many people remember this, but decades ago you could just buy a prepaid mobile SIM and immediately use it, no legalities involved.
If you lose it and someone else gets it, tough luck! That's the cost of freedom.
These days KYC is required for every prepaid SIM. If you lose it, it's easy to prove you're the owner and get it back.
And on top of that, many famous services (Google, Facebook etc.) ask for your mobile number... why is that? Well, tracking becomes easier. They can associate phone numbers with social media profiles. You gain safety, but you lose freedom.
I don't believe people should depend on anyone's "moral compass", because it's highly subjective from person to person.
If you want something objective, the rule of law would be more appropriate.
As I said, I wouldn't mind KYC if it was optional, but it's almost always mandatory.