"I declare the Worst Argument In The World to be this: 'X is in a category whose archetypal member has certain features. Therefore, we should judge X as if it also had those features, even though it doesn't.'"
This recalls many cases on Hacker News when someone has disagreed with someone else by saying, "Your argument is an example of [name of rhetorical or logical fallacy]." Perhaps it is carrying out the worst argument in the world to identify one part of someone's statement as a logical fallacy, if the fallacy doesn't vitiate the statement, and if sound evidence is still in view to support the statement. Sometimes facts of the world are as they are even if they are mentioned by people who argue inaptly, so it would indeed be a bad argument to ignore the message because of infelicities of expression by the messenger. If we look at pg's essay "How to Disagree,"
http://www.paulgraham.com/disagree.html
we see advice that a better way to disagree is
"Refuting the Central Point.
"The force of a refutation depends on what you refute. The most powerful form of disagreement is to refute someone's central point."
So I guess my central point here [smile] is that while it may be interesting to identify a general form for many particularly bad arguments, it is even better to be specific in grappling with the evidence for the core factual assertions of the person with whom you disagree. That takes abundant knowledge of the world, and a willingness to look up facts. I always appreciate people on Hacker News who can point to carefully gathered facts, analyzed by people with appropriate domain-related knowledge, as we discuss issues here.