Don't worry. No one actually booted you.
The server has what's called a Dead Spot issue from time to time.
This is when the server shows that it has at least one empty player slot but yet no one can join the server in that empty slot.
If you join the server and as soon as the map finishes loading up on your end, you are immediately "Booted From Session" this is due to a Dead Spot. No admin can boot you that fast. The server just wouldn't allow anyone else to join for some reason.
If you were banned for glitching, it would say you were "Banned by Host" before you are even able to join the server.
Most times this Dead Spot issue clears up once the next map starts. Sorry for the inconvenience.
Thanks for Playing in the Arena!