Guilt by Association

An argument is rejected because it is, was, or can be associated with a bad person or entity.

Examples

Pol Pot once said that 1+1=2, therefore obviously 1+1 must not equal 2, because Pol Pot said it!

The Reichstag fire was caused by Communists because, as our dear leader Adolf Hitler has explained so that even a fool can understand, the simpleton found outside the burning buildings, who surely did the deed (because we say so), once went to a Communist meeting of some type. Therefore all Communists are guilty.

Fred is guilty of eating the cookies, because although he was nowhere near them, he does nevertheless associate with thieving Sponge Bob fans.

Weaknesses

Just because a person or group makes a statement, that does not make the statement false. You can easily point this out by giving an example like those above.

Just because a statement refers to a person who is associated with something you don't like, that doesn't make the statement automatically true or false.

You can also attack the notion of bad, which is a relative term, as is good. What is bad to one person is not necessarily bad to another.