The author endorses racist/sexist views, comes out for child labor, and incorporates those themes into their work, or somehow publicizes that fact in relation to your property. The details don't matter to 99% of the people out there, if an official Doom product endorsed racism, Bethesda would definitely be dealing with the fallout.
I'm not sure how likely it is factors all that much. When you have a hundred million to billion dollar business, why risk allowing anything even remotely like that which might harm your brand? It's much easier to just say no.
