There is just one thing i can say.Anything that does not belong to you that you take away is considered as stealing wether it is physical or virtual
Yes but what more important is it is all about business matter. Stealing in the sense of making wise by someone like winning in the gambling, profiting in investing and trading off good in trading makes good way of stealing. But when you say hacking or fooling someone it is not acceptable it is bad stealing. Therefore there is two way of stealing.
I agree, take away something doesn't belong to you is stealing, an illegal activity and could get you into the jail. You should consider about being a victim of bitcoin stolen before want to take other people has.