I was reading slush and an author inadvertently (I assume it was inadvertent) offended me with politics. As I'm using the word, politics can cover a myriad of topics from Democrats and Republicans in the USA, other political entities in other countries, to different religions, to various companies (Coke versus Pepsi, anyone?). Authors don't necessarily know an editor's affiliations. Thus, authors run the risk of offending them when they write a story with a negative slant to one 'political' party. Bottom line: I rejected that story.
What's a poor writer to do? Use his/her imagination! We are talking about fiction here, folks. I have no problem reading a negative story about the Remocrats or the Depublicans, for example.
Of course, writing is a creative endeavour, so if your story demands 'political' negativity, go for it. Just don't try to sell it here.
Good luck with your stories, positive or negative, political or apolitical!