Guilt by association

Examples:

1. Atheism must be wrong, because Karl Marx and Stalin were atheists, and just look at them.
2. Anne: "Wow - that's a great word-processor". Bill: "Yes it's Microsoft word". Anne: "Well there must be something wrong with it then, because Microsoft use unfair business practices"
3. Anne: "I think that there should be heavier penalties for drug-dealers". Bill: "really, that's a BNP policy! You don't want to support those racists do you!"