After you write and publish a book, it seems like friends, family and colleagues come out of the woodwork. Hopefully, they send along kudos and congratulations. However, there are those curmudgeons who take it upon themselves to put down your successes and efforts. Unfortunately, negativity goes with the book marketing territory.
I tend to ignore the Negative Nellies and Neils of the world, but sometimes you have to fight fire with fire -- in a positive way.
My number one suggestion to authors who handle their own marketing is to make sure you have a solid online presence. Maintain a strong author brand that stands out in an engaging way. You don't need to spend thousands on a website, but make sure your site is filled with positive book reviews and testimonials -- that's the best place to start.
The BEST way to handle negative criticism on the internet is to counterbalance with positive press and reviews. If you sell your book on Amazon or Barnes & Noble, check customer book reviews on a daily basis and respond immediately to negative attacks. If appropriate, I recommend including links in your comments -- directing people back to your website, positive book reviews, etc.
Remember to be respectful and courteous, even if you disagree with the person's negative comments. Everyone loves to be a critic, and people love drama. Just don't give into the drama and remain level-headed and leave your emotions out of the equation. I've had my share of online attacks and criticism, and the storm eventually passes -- people become bored and find another target.
The reality is that NOT everyone in the world is going to love your bok. People love to state their opinions (both good and bad), so be prepared for whatever comes your way. Don't wallow in other people's negativity. I have seen this happen often with self-published authors. They become frustrated, throw in the marketing towel, and give up altogether. They take the criticism to heart and go into hiding.
Remember to consistently stay on top of your online reputation, and you will be ten steps ahead of your book marketing...and the negative naysayers!