Any tips for what an EU citizen can do against this, beyond upvoting this story on HN?
To make it a low-cost effort, we could (a) prepare a list of relevant politicians (b) create a template of the letter. Then our non-technical friends need only sign and mail this. And if we put this all up as a one-pager on GitHub pages, it's suitable for sharing on social networks too ;)
You can read the derogation here: https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A... . There is a somewhat helpful first page that provides context.
Personally I think it is quite a reasonable derogation; the pirate party clearly disagrees.