She revealed earlier this weekend that she had PTSD from 'watching friends being killed by the police.' Famous friends: Tiffany Haddish, 40, was joined by her quarantine buddy Common, 48, at a Black Lives Matter protest in Los Angeles on Sunday, where they met up with Megan Thee Stallion, 25 Tiffany was holding back with her white 'FedUp' T-shirt, designed …