How would you react if you found out someone plagiarized your work and published it?
This actually happened to me in a very small way.
For a number of years I coordinated the dealers' room for one of our local conventions. I wrote the blurb for the dealers' room page for the website.
Some time later I took a look at the website for a small start-up convention in the area and I noticed that the blurb for the dealers' room sounded a little familiar.
Yup, it was my blurb with just the dates, times and prices changed. I used a rather distince, conversational style, so it was really not likely that it was coincidence.
I didn't do anything about it except mention my amusement to a few people. And when the con crashed and burned spectacularly the next year I wasn't a bit surprised.