Good article from The Passive Voice blog on negative reviews on Amazon and such. This struck me in particular:

Then comes the first negative review from Jeremy, from Hounslow. Your brain immediately reacts by telling you that Jeremy must be mentally ill. Then you decide he must be a troll.

The most stinging review so far to Dragon’s Danger wasn’t from a troll. This is spot-on, the reviewer was giving me an honest opinion. My problem was the extent to which I thought she was off-base.

Still, the thing you have to do is stay quiet! Don’t comment. Leave it be.