Hateful conduct: You may not promote violence against or directly attack or threaten other people on the basis of race, ethnicity, national origin, sexual orientation, gender, gender identity, religious affiliation, age, disability, or disease. We also do not allow accounts whose primary purpose is inciting harm towards others on the basis of these categories.
The problem is that we live in an age where just about anything you say could inadvertently offend someone. As Starbucks learned, a simple red cup was enough to offend a handful of Christians. A simple “Merry Christmas” could offend thousands of others.
Twitter does a crappy job of being transparent with how they make their decisions. I understand those accounts who accomplish nothing more then attacking others.