Hey,
I'm insensitive and rude! We curmudgeons need love too!
If a book is terrible, people have just as much right to say so -- and to say why -- as they do to praise it if it is great. Yes, an actual person worked hard on that book, but I guess I'm too old-school to judge on effort rather than results. If you hire a guy to fix your roof, and when he's done, despite how hard he worked, it leaks worse than it did before he started, will you be satisfied with the job he did? Is the hard work sufficient? Are you going to recommend him? Or are you going to warn off your family and friends, because no matter how hard he works, the roof still leaks?
Writing for publication isn't putting your child on display to the world; it's putting your commercial product on the market. Any writer who mistakes the former for the latter needs to restrict his or her writing to friendly literary journals, or perhaps passing around among close friends. The market treats books as commodities and writers as manufacturers, and that hard work is of no more importance than that of the people who worked equally hard on
The Last Airbender, which is currently in single digits at Rotten Tomatoes.
There are two kinds of criticism. One is the "your book isn't what I wanted it to be" variety. The other is the "your book has flaws, and this is what they are" variety. Foolish writers either take both to heart or ignore both. Wise writers disregard the former and learn from the latter. Whether or not the reviewer was "gentle" about it should not matter in the least.
P.S. I just bought the book on the theory that anything that ticks off a religious whacko that much has to be worth reading.