Package deal fallacy
From Wikinfo
The logical fallacy of the package deal consists of
assuming that things often grouped together by tradition or
culture must always be grouped that way.
It is particularly common in political arguments: "My opponent is a conservative who voted against higher taxes and welfare, therefore he will also oppose gun control and abortion." While those positions are often grouped together as "conservative" in American politics, there's really no reason someone couldn't approve of some but not others.
References
- Adapted from the Wikipedia article, "Package_deal_fallacy" http://en.wikipedia.org/wiki/Package_deal_fallacy, used under the GNU Free Documentation License
