The “I just write what I know” defense is also rather specious—taken to its extreme, it’s absurd. Novelists who write historical fiction aren’t time travelers, nor did George Lucas exist a long time ago, in a galaxy far, far away. Writers are only limited by their imaginations and prejudices. A showrunner doesn’t walk into the writers’ room on the first day of work and have it suddenly dawn on her/him that s/he’s only hired white people. These are deliberate decisions, so own them.