Taking a step back, this is a matter of once bitten, twice shy. DWS and KKR have been screwed by the trades, they are down on the trades, though KKR is a bit more balanced in her printed views. But, it's very much a caveat emptor situation. In fact, we do this every day in our personal lives, though it's often not PC to say so.
I know a guy who's been victimized by criminals several times, who always happen to be Hispanics (due to location and demographics, mostly). But now, he's unabashedly anti-Hispanic, not able to psychologically separate out the criminal element from the general population.
I only say this as an example, so please let's not get off track too much talking about social issues.
The point is, people often reason from the specific to the general, and there's some truth to it, though less truth than instinct indicates. If I always have a bad experience at (say) my local Burger King, I may avoid Burger Kings entirely, even in another city, and that may make sense. How much is the local issue, and how much is the franchise food itself?
If I was bullied by football jocks in high school, maybe I'll hate football, jocks, or both.
And, getting screwed by agents and tradpubbers might, unsurprisingly create an anti-trade blogger-author.
Same thing if people happen to read too many crappy indie books--they think all indie books are crappy. And, there's probably statistical truth there, if only because anyone can self-publish.
What's ironic is, we all tend to do it, and justify it, when we're the "discriminator," but we decry it when we're the target of the discrimination. It takes some self-examination and thought to step back and try to be fairminded in all situations.