I'm not sure whether I agree with this, or disagree. I can kind of get the reasoning about it, and I agree with writing reviews that are constructive...but not writing a review about a bad book? Not buying it.
When I write a review, I try to touch on both the positive and negative. Generally there is at least one good thing about the book, even if it's kind of lame (oh, the cover art is pretty!).
I really try not to be snarky when I write a review. If a book is bad, I might become snarky in the process of reading it to let off steam, but if you are trying to write a legitimate review, leave the snark at a minimum.
Sure it's great to avoid authors that are known to behave badly...but why not just let karma do it's thing. There is a fine line between Authors behaving badly, and reviewers/readers behaving badly. If you leave a one or two star review and someone does not like it and attacks you for it...smile, report and walk away. Do not engage. I repeat, do not engage. All this does is make us band of reviewers look bad. Instead, if you cease to engage, it makes the BBA look like BBA.
Sure, you can warm people that certain authors have bad reps...but if you can, do it privately. This isn't high school. Besides, why would you want to draw attention to bad authors? Put energy into promoting good authors. If no one knows about bad authors, all the better. But if you never promote the good ones...no one will ever know about them. And that would be a shame.
In general, just be decent human beings. Respect goes a long way.