Agreed. A situation similar to this happened to me with Steam over a payment issue with their service. They banned me even though I had thousands of dollars of games and an account since Sept 2003. I had to go to my bank and escalate multiple times to get letters providing the info steam wanted about my account and credit card to prove it was legitimate. Eventually after contacting them enough times they said they would do a "one time good faith" gesture by unbanning me but warned if it ever happens again they cannot help and that my account will be flagged with this. In the end I didn't do anything wrong and the bank didn't do anything wrong, it was all on steam. It was over $10 by the way.
Sadly, the real issue here is with the banks and the payment processors. It's very likely that they have metrics for larger marketplaces about being below a threshold for fraud. Online game stores like steam live, breathe and die by payment processing.
This was the reason why free trade was removed from RuneScape back in the day and it wasn't even a Jagex issue. People would go to 3rd party gold selling websites and then pay for gold with stolen credit cards. They could easily keep the money because the trade cannot be reversed without a moderator and what they were doing was against the rules so everyone would just get banned. The payment processors saw a bunch of fraud related to a game called RuneScape and told Jagex if they dont fix this then they will be blacklisted.
Which goes to show, being the nice Linux guys doesn't change they are a corporation like all others, and will behave exactly the same.
Buy from GoG instead. It's better. At least you can download the install files and don't need to install any 3rd party software to login to play them. I have 200+ games on Steam but I have ceased purchase on Steam.
There's also grey areas with Steam like when you buy a Steam key for a game outside of Steam through places like GreenManGaming and get your reviews discounted or otherwise flagged arbitrarily based on an opaque authenticity heuristic.
They've made it clear that you don't own your cloud library, so the only reasonable answer is to never pay for something with DRM you cannot remove (including things that require an online account for functionality you consider important), and treat services like Steam as a temporary convenience to download known good files that you then fix to remove any DRM. If you only treat these services as a download tool, their ban loses all teeth.