No. Invalid comparison. If you legitimately discover a cryptocurrency wallet private key by sheet lucky, and such cryptocurrency has no backing = is based in pure thin air, such as the case of Bitcoin, and there are public nodes which doesn't require you to abide by contracts that would forbid you to do so (which is supposedly all nodes), you're good to use that as you wish and it won't be a crime.

It's unethical to steal something tangible. Bitcoin has no tangibility whatsoever. You can't steal it.