Another point, no one was banned for having 18+ content. They were ALL suspended for exactly 3 days by the same GM for this exact reason:

3.3 Profanity and Offensive Language. You may not use profanity or any language that a reasonable person would find offensive.

There are separate points in the TOS that talk about violating the ESRB rating so why weren't those listed? If that was truly the offense why does a GM, of all people, need to hide behind this reasoning instead?