True, but we are not concerned with quantity here, as we would be if we used "da"
Are you saying that anyone who speaks Esperanto must be a nerd? That sounds like a sweeping generalisation to me.
The pun in English is that a "club" is either a group of people or a blunt weapon so the added clause, having tacitly noted that "tio klubo" is the first kind of club, then proceeds based on the same pun working in Esperanto to say that it is not the second kind. Of course, Esperanto may have an entirely different word for blunt weapon.