So why not encourage GPL violators ("pirates" too)? Instead we seem to cheer whenever we find a GPL violator.
First, we should understand what the propagandistic term "piracy" really means and understand that meaning as separate from sharing—a friendly, neighborly thing to do. As the GNU Project points out in it's list of terms to avoid on "theft": "In general, laws don't define right and wrong. Laws, at their best, attempt to implement justice. If the laws (the implementation) don't fit our ideas of right and wrong (the spec), the laws are what should change. A US judge, presiding over a trial for copyright infringement, recognized that "piracy" and "theft" are smear-words.". This difference gets to the heart of the problem in your point—you're conflating the legal with the ethical and then trying to get others to view all sharing as copyright infringement and all copyright infringement as equivalent because the law frames things in that way.
We should recognize that the terms of the licenses involved between, say, the GNU General Public License (GPL) and a typical Hollywood movie, are radically different when it comes to doing what friends do: share. One can and should share copies of GPL'd programs. It's easy to do, the GPL is easy to comply with simply by also sharing a copy of the complete corresponding source code of the program at the same time as one shares the binary. By contrast, other famously shared copyrighted items (such as most Hollywood movies) aren't legal to share even if done non-commercially and verbatim. So doing the thing that comes naturally with friends, non-commercial and verbatim sharing, is likely not allowed by that movie's license.
Since you mention the GPL, a free software license written by Richard Stallman, this is somewhat akin to what Stallman describes in his talks about the freedoms of free software specifically freedom #2: the freedom to help your neighbour. That's the freedom to make copies and distribute them to others, when you wish. This comes from a 2006-03-09 talk and you can see how the consideration here is akin to the dilemma one faces should a friend ask for a copy of a Hollywood movie:
Freedom two is essential on fundamental ethical grounds, so that you can live an upright, ethical life as a member of your community. If you use a program that does not give you freedom number two, you're in danger of falling at any moment into a moral dilemma. When your friend says "that's a nice program, could I have a copy?" At that moment, you will have to choose between two evils. One evil is: give your friend a copy and violate the licence of the program. The other evil is: deny your friend a copy and comply with the licence of the program.
Once you are in that situation, you should choose the lesser evil. The lesser evil is to give your friend a copy and violate the licence of the program.
Now, why is that the lesser evil? The reason is that we can assume that your friend has treated you well and has been a good person and deserves your cooperation. The reason we can assume this is that in the other case, if a nasty person you don't really like asked you for help, of course you can say "Why should I help you?" So that's an easy case. The hard case is the case where that person has been a good person to you and other people and you would want to help him normally.
Whereas, the developer of the program has deliberately attacked the social solidarity of your community. Deliberately tried to separate you from everyone else in the World. So if you can't help doing wrong in some direction or other, better to aim the wrong at somebody who deserves it, who has done something wrong, rather than at somebody who hasn't done anything wrong.
However, to be the lesser evil does not mean it is good. It's never good - not entirely - to make some kind of agreement and then break it. It may be the right thing to do, but it's not entirely good.
The only thing in the software field that is worse than an unauthorised copy of a proprietary program, is an authorised copy of the proprietary program because this does the same harm to its whole community of users, and in addition, usually the developer, the perpetrator of this evil, profits from it.