Depends on what your entire diet is. If you are eating only peanuts - or anything else - that is bad. If you eat a handful of peanuts once in a while that is fine. Even a cookie every few weeks is fine, but 6 cookies a day every day would be bad. Someplace in between is generally a good place to be.
I'm assuming of course that you are "normal". If you are allergic to peanuts they are of course worse than a cookie. If you are diabetic cookies are bad.