How would you react if you found out someone plagiarized your work and published it?
This is a loaded question, specifically because of the word 'plagiarized.' It implies ownership of ideas, which is a flawed premise.
Imagine if you had to credit (and possibly pay patent licenses for) the work of every single mathematician back to the origins of human computing every time you did a basic operation. Or, imagine if you had to credit the inventor of every single word you used in every document you write. Imagine if artists had to credit the original discovers of basic shapes, human proportion, and color. Imagine if musicians had to credit not only the inventors of their instruments, but the notes themselves, the rhythms, and even musical genre concepts and styles.
Imagine© a© world© where© every© last© idea©, concept©, and© mental© construct© was© owned© and© required© accreditation©.
The fact is that at some point, everything made public becomes general knowledge. We all copy the works of others on a minute to minute basis inside our minds and in our lives. If you've ever done mental addition, or figured out the area of a square, spoken a word you did not personally invent, hummed a song you heard on the radio, or tapped out a beat with a pencil, then you've copied someone else. Your basic vocabulary, your understanding of colors, mathematics, all of these ideas are directly copied from the people who originally raised you.
The actual problem is greed. A person wants their ideas and creations to be considered valuable, so they can convert them into money or power. The question is a matter of when something become general knowledge, and how much the new idea was actually worth. Relative to the immense pile of basic *shared* human knowledge required to invent and convey a new idea, the work of any individual is trivial, and thus the concept of "plagiarism" itself is hypocritical.
To answer the original question, work I have done is *copied* every second. For example, I've contributed to the Linux kernel, so if you've got a router in your house, or an Android phone, or certain models of TVs, or any of a wide variety of other electronics, then you personally have a copy of my work. Is that plagiarism? Does it entitle me to anything? Of course not. My work was done for my own benefit at the time and the fact that it may have benefited others is simply a happy side-effect, and I was only able to do it in the first place because of the collective knowledge of literally millions of other humans before me.