In these instances, to fix the tone, you have to fix the way you think about a given subject. You have to back off, calm down, see other points of view, maybe even take some responsibility for whatever happened. When writing about such delicate subjects, you must not let a negative tone take over by ascribing motives to people: You just tell what they did, and let the reader read motive into it. You must write with forgiveness, understanding and humor. In some ways, this can be a payoff to examining your tone as you write: You change the writing, and the writing changes you. But if you find this is not possible with your subject, don’t be afraid to scrap a project that you discover has inherent problems with tone. You’ll be a better writer for it.