Genetic FallacyFor some reason I was thinking the fallacy was called ad hominem, but that's actually somewhat different, but similar since the focus is on who not what and when we think logically the who of an issue seldom is relevant.
The genetic fallacy, also known as fallacy of origins, fallacy of virtue, is a fallacy of irrelevance where a conclusion is suggested based solely on something or someone's origin rather than its current meaning or context. This overlooks any difference to be found in the present situation, typically transferring the positive or negative esteem from the earlier context.
LINK:
http://en.wikipedia.org/wiki/Genetic_fallacy