Jew rank is a moderation feature, not a discrimination mean...
Server has strict rules regarding its "RP" mechanics (for example restrictions made to killing others). Every player is informed about this fact on server join, by clearly visible messages. Sadly many new visitors completly ignore infos, and go into murdering rampage. Now, before introducing Jew rank, they would simply met with considerably long ban. This would be also case for chat spammers, extremly toxic players or various trolls (TNT triggering etc.).
Jew rank allows those players still play on server, while hindering their toxicity/trolling/rule breaking capabilities. Those limitations include chat cooldown, inablility to use TNT, and so forth. It allows player to reedem themself by behaving properly as Jew, and speed up unbanning process.
So as you see, our friend Akiba356 is just common rule breaker, that got mad by his punishment, and wanted petty revenge.