I'm also not sure of the value of the Dislike option. I can't think of a case when I would want to use it. It may be part of the whole thank/like/dislike structure and can't be separated.
But I did find one related setting. If you click on Settings in the top right of this web page, then go the the bottom of the "My Settings" panel on the left of the page, click on DBTech - Post Thanks/Settings, then next to Dislikes you can disable the postbit settings for Dislikes. This basically means that if someone clicks on the down arrow in your ID at the left of a post, the dislike information is not shown. (Try it on mine.)
Not exactly what you asked for, but something.