I found this blog post about an author defending her work, anonymously, against a critical review. It escalated quite a bit, even after the author was identified. Although she eventually deleted all her posts, they were archived elsewhere by interested parties. You can read them if you want, or just read the comments in the article, such as this, from author Neil Gaiman:
And yes, it's a horrible car crash, and I post it here not because it's funny in an Oh God Make It Stop kind of way, but because, if any of you are ever tempted to respond to bad reviews or internet trolls etc, it's a salutary reminder of why some things are better written in anger and deleted in the morning.
I had an experience something like this not long ago, when I compared two products in an online review. I thought the review was unoffensive, but the seller of the losing product contacted me at my home email repeatedly, and had many unpleasant things to say in print on the website, as well. Rather than politely ask me to reconsider, she went ballistic, even accusing me of working for the competitor. I'm not even in the same state. So I know a bit about this tendency to feel like 1) we are writing for ourselves, although the internet is very public; and 2) we can reach through the internet to directly contact a person with whom we disagree. The internet gives us a false sense of intimacy with strangers. How far we take that is something that not everyone agrees on. Even famous authors (Anne Rice, Alice Hoffman, Alain de Botton) have reacted in this way.
I think that doing so breaks an unspoken agreement about how far we may go and in what venue. While in my case, the seller's comments on my review were nasty and her comments about the competitor even actionable, the thing that really bothered me was that she looked up my personal information and contacted me directly and angrily. She also has my home address, since I had the product shipped by ground delivery, something you might consider not doing with with individual sellers on sites like Amazon or ebay, and something I will never do again. From now on, everything goes to the PO box.
"Immersion in the life of the world, a willingness to be inhabited by and to speak for others, including those beyond the realm of the human, these are the practices not just of the bodhisattva but of the writer." --Jane Hirshfield