Using a certain pattern in a Poisoning the well argument that ascribes a negative attribute to opponents is a false dilemma, an informal correlative-based fallacy.
In this pattern, an unfavorable attribute is ascribed to any future opponents, in an attempt to discourage debate. This is a false dilemma: not all future opponents necessarily have the unfavorable attribute. A false dilemma (sometimes called false dichotomy) is a type of informal, correlative-based fallacy in which a statement falsely claims or assumes an "either/or" situation, when in fact there is at least one additional logically valid option. 
