An association fallacy is a type of logical fallacy which asserts (or implies) that qualities of one are inherently qualities of another, merely by association. It sometimes referred to more specifically as "guilt by association" or (less commonly) "honor by association". When applied to personal reputations, it is also a form of reasoning by reputation.
It also seems to come into play with regard to helping people who are experiencing hardship: the thinking seems to be that if you help someone, whatever problems they've been dealing with may become your problems as well – as if their troubles were an infectious disease. This mentality may also be rooted in zero-sum thinking, where there is a belief any help one person gives another is going to cost the giver as much as it benefits the recipient (and thus providing no net social value), ignoring the existence of marginal value.
Conservapedia: see Guilt by Association dKosopedia: no equivalent article (as of 2008-05-06) SourceWatch: no equivalent article (as of 2008-05-06); see Transfer