It's also a feature explicitly required by both the Apple and Google app stores for apps that have user generated content.

https://developer.apple.com/app-store/review/guidelines/

1.2 User-Generated Content
Apps with user-generated content present particular challenges, ranging from intellectual property infringement to anonymous bullying. To prevent abuse, apps with user-generated content or social networking services must include:
...

• The ability to block abusive users from the service

https://support.google.com/googleplay/android-developer/answer/9876937?hl=en

User Generated Content
User-generated content (UGC) is content that users contribute to an app, and which is visible to or accessible by at least a subset of the app's users.
Apps that contain or feature UGC, including apps which are specialized browsers or clients to direct users to a UGC platform, must implement robust, effective, and ongoing UGC moderation that:
...

• Provides an in-app system for blocking UGC and users;

Every day he further proves that he has no idea what he's doing. He's 100% going to reverse this decision when he find out all of the things he should have know before saying anything.