Their priority is to reduce the spam on their email platform for their customers—their goal isn't to prevent you from sending emails.
Spam is a serious problem. They don't blacklist lightly. It's their way of trying to identify and prevent real problems.
Blacklists are legal because they are designed to prevent fraud or other activity that disrupts normal business. We all need to accept that fact.
If you made a mistake and were blacklisted, don't make the same mistake again. You likely won't be forgiven a second time.