I agree it is silly to go around telling people something doesn't exist, and equally as silly to say something does in the absence of any evidence. In fact going around unsolicited telling people anything is an act of ego.
Athiesm is the the absence of belief in a deity, it just follows that it will take the form of the antithetical position to deism. As to a logical weak position I would think the lack of coraboratory evidence would put the deist in the weak position, and pointing out to someone how they are wasting their energy in a delusion a matter of charity. The futility of such, notwithstanding.