Probably saying something against the Terms of Service
Completely forgot about this. This could definitely be a reason. Kabam didn't care at ALL what the playerbase was doing, so long as it didn't hurt the game's revenue in a significant manner. However, I guess DECA cares about this kind of stuff now.
Edit: Given thought, I do remember a time when Kabam would change player names and guild names if they were inappropriate, but I don't know about banning people like DECA has done in the past with "JewElimination"