There are instances where people use wordplay to gain an emotional/rhetorical advantage in a debate. For the seasoned, this might be irksome at best, but I agree, repeatedly hearing "Dumbocrat" can get old and I, for one, will quickly lose respect for that person. But comparing Stallman's use of the word "used" to conventional, quite childish wordplay seems like a very, very far stretch.

Stallman is redefining those people we know as "Facebook users", because in this case, "user" is not a correct term. A user is someone who uses a product to gain utility. By using a product, you gain something from the experience. A used is someone who is on the opposite end, where you are on the losing end of the deal.

In a relationship between Facebook the corporation and the Facebook "user", who is gaining more utility, and who is on the losing end? Stallman argues that Facebook "users" are on the losing end. Thus they are appropriately termed "useds", with evidence backing his redefinition.