That case in the zoo is trespassing, not stealing. Trespassing is far less of
an offense than theft.
I heard some months or maybe a year ago that an Australian court decided that
copyright infringement is more like trespassing than theft. Well, that's
true, but it's still not comparable. Trespassing into a zoo takes up space
that could be occupied by others. When you copy your copy, you are
theoretically using your own tools on your own computer, or you are paying
somebody else to use their tools on their computer. The only thing similar to
trespassing is using someone else's server without their permission, such as
downloading something from the server without permission, because servers
have limited resources that have to be used to fulfill all requests; if you
download something without being authorized, authorized users could have to
wait longer for their downloads to finish.
In fact, the only thing copyright infringement is comparable to, because this
is what it is, is competition. Copyright is just a legal monopoly, i.e.
competition is not allowed.