Free? You are feeding them valuable information about the descendants of the ancestors in their registry. Regardless of your personal feelings on the topic of re-baptism, your relatives may not share those sentiments. Out of respect, you have an obligation to advise your living relatives that their names have been turned over to the Mormon Church which may use that information for religious practices.
That is horse poop, you got to be dead to be rebaptised and you have to have LDS relatives. In the main you have to be an Ancestor of an LDS member to qualify.