Right along those lines comes a story from the early 1900's. Yes, this is a true one.
A man walks into a cigar store and points to a five cent cigar. He's dressed nicely, acts normally, and the clerk hands him the cigar. The man gives the clerk a five dollar gold coin, and the clerk gives the man $4.95 in change.
Except for one thing... that five dollar gold coin is actually a V-nickel (also known as a Liberty Head nickel that was gold-plated. The gent goes around and drops a lot of the gold-plated nickels until he's caught.
The man goes to trial, and is found not guilty.
How, you ask? The gent turns out to be a deaf mute. Some racketeers gave him the coins, and the gent went around buying nickel cigars. The racketeers got most of the take. The gent was found not guilty because he never spoke, just pointed to the nickel cigar. The clerks did not look closely at the coins. The gent was under no obligation, according to the legal folks, to tell the clerks they made a mistake.
OK, obviously the gent knew what he was doing. But he got away with it. Does that make it right? Certainly not, and I think that that verdict would be very different if it was tried in modern courthouses. Moral and legal may not be the same thing, but it certainly takes away from someone else, even if you can't see it directly. That $700 that your brother made while sitting in front of a grocery store could have kept a family in a shelter, or fed a bunch of starving folks.
By the by, you can sometimes find gold-plated V-nickels at coin shows.