It should be, but it won't be. It's all written in the user agreement, which no one reads and everyone agrees.Losing access to your entire digital library due to a ban should be illegal, regardless of the platform. This is insane.
In this case, I would recommend contacting Reddit - Stellar Blade, since the ban was received through their game. If possible, interest their community manager, most likely they will ask to provide all the information and a screenshot. But I think if they don't see anything scary in your post, they will be able to make a request to Sony and unblock your account, provided of course that you didn't write any nonsense in the post =)