I recently reviewed a book that was ostensibly about racism. I was excited to read it--the author appeared to have a strong point of view and a sharp sense of humor. He was African-American, and the book was going to address racism he experienced from white coworkers, but also mistreatment his lighter-skinned wife experienced from African-American women with darker complexions. I had hoped for a detailed explanation of this phenomenon, because it's so confusing to me. For the sake of argument let's just cede the point that white people are blue-eyed devils; if that's true, why is lighter skin "better"? And apparently also much worse? Way over my head. So I was eager to dig in.
Unfortunately, the book was fairly useless--so full of typos and run-on sentences that it was bruising to get through. The author further complicated the experience by using examples to illustrate his arguments about racism that weren't well explained; they came across as both petty and paranoid. Let me be clear: I have no doubt that he's experienced racism and that it was awful, but he didn't tell the story of it understandably. It was as if he was pointing to a cardboard box and shouting, "See?!" but the box was empty.
As for the elderly women who said snarky things about his wife's skin color, he spent twenty pages attacking them with some of the ugliest language imaginable, which makes their teeth-sucking disapproval seem petty and fairly benign. Something about a grown man disrespecting an older woman like that was deeply off-putting as well. Disagree and disapprove, sure, but don't rip her to shreds with references to incontinence and frailty. That makes you the bad guy.
These factors all contributed to the book being a disappointing downer, but the author lost his remaining credibility when he peppered the book with a bunch of sexist and homophobic remarks. As a gay woman of course that's going to irk me, but my objections aren't simply personal. If you're making a case against prejudice, holding yours up as the only one that deserves sympathy while you exhibit prejudice toward others doesn't fly. It instead raises the question, "Why should anyone listen to you?" and risks reinforcing the original bias you were so upset about.
Let's look at an abstract example. If I make a feminist argument against sexism, you can accept or argue with it based on my thesis. If I make the same argument, then use it to call out women of color for failing to go along to get along with my prefab white brand of feminism, two things happen. First, I reveal that I'm an ignorant bigot, which undermines any critical thought I've used elsewhere in the argument. And second, I've weakened my point, both by watering it down and revealing my inability to think beyond the tiny circle of my own limited life experience. If I'm only talking to myself, job well done, but that conversation doesn't need to be repeated or make it into prin.
If you're writing about religion, politics, race, class, diet, or any nonfiction topic that tends to rile people up, it's tempting to be inflammatory because it gets attention. If that's all you want, godspeed, be as offensive as you like, but don't whine when the consequences catch up with you. For the rest of you I recommend moderation in tone and respect for all in your content. And take a look at yourself. Allow for the notion that you may not be the best person to make the argument you feel so strongly about (There are a lot of books I will not be writing for this very reason). Lead with your intelligence and humility, and if you have none of either, consider waiting a while before committing your thoughts to paper. Let yourself earn some wisdom first, and we'll look forward to your take on things.