Piracy is not theft, but it IS unjust enrichment
Piracy-as-theft is very, very rare - it means you don't have your copyrights any more. That's not to say that piracy is right, it's just not theft. The analogy I usually use is a bus or train fare - you are consuming a service (use of the train / software) without paying for it. When you buy software you are *not* buying a good, you are buying a *service*. "Intellectual property" is the right to be paid for services rendered.
IP generally can't be "stolen" as the original owner does not lose anything except the possible revenue stream from the IP. (To "steal" is to "take... property wrongfully" according to Mirriam-Webster; if the original still exists it has not been taken, just copied.)
"Possible" is a key word here however - anybody who thinks every pirated item is a lost sale needs a serious reality check.
Protection from piracy is really only practical at a limited level - you can stop Bob from giving Anne a copy of your software by copying the CD, but you can't stop the professional pirates who reverse-engineer your code and remove the copy protection code. The only practical way around this is to have your program require - not just for the copy protection check but actually REQUIRE - an online connection to a server thant can check the legitimacy of your software.
This model works for network-based applications (and games) but not for a lot of other software, although software can be written to run an initial check when it starts up. Many games use this model.
The flipside to this is that if your software will only work when it can connect to a particular server, and you then turn off that server, you are depriving the purchaser of a service that they have paid for, and YOU are the one who is "stealing". You can supply a patch to "fix" this when you are turning your servers off, and I know of at least one company that actually went ahead and did so.
The thing about copy protection is, you have three categories of people using your software. There are the professional pirates, whi will remove the copy protection. There are the people who would pirate your software if they had the technical nous, but buying it is cheaper than the associated hassle. And there are the people who are willing and able to pay you, and don't want to pirate your software. This third category is your core customer base, the people who actually pay your bills, and your copy protection is punishing those customers (as well as the category two people who don't want to pay you).
Suffice to say that there are bastards on both sides of this particular divide.