There’s a brilliant Twitter feed called @AvoidComments whose sole purpose is to remind us not to read comments on the Internet:

Don't Read the Comments

This is excellent advice when it comes to newsy sites like Salon, which seems to be where repressed rage goes to die seethe indefinitely. And even Justin Bieber knows not to read the comments on YouTube: “I don’t read YouTube comments because those can get you sad.”

Justin Bieber Doesn't Read Comments

Seriously though. I have a love-hate relationship with comment streams. The quality can vary so widely and it usually depends on what kind of atmosphere and community the blog owners cultivate. I love sites with upvoting systems that allow the best comments to rise to the top and which encourage regular commenting and conversation – see SEOmoz, Reddit, and XOJane, where I’ve lost hours of my life poring through user-generated magic.

But no blog or website is immune to comment stream idiocy. Allow strangers to plaster their thoughts on your Internet space and some of those thoughts are doing to be variously dumb and outright offensive. Much like lukewarm casseroles at a potluck are breeding grounds for bacteria, comment streams seem to be breeding grounds for obnoxious and illogical arguments. That’s why we have Godwin’s Law, which states that “As an online discussion grows longer, the probability of a comparison involving Nazis or Hitler approaches 1.”

Godwin's Law of Blog Comments

When entering any argument or debate, it’s always good to be armed with a solid knowledge of logical fallacies – those nefariously common pitfalls of the human mind, patterns of thought that we all slip into that are nevertheless dead wrong. Being familiar with these fallacies makes it easy to call out your opponent when he’s making a right fool of himself. This is especially true in the battlefields of comment streams, where people are approximately 200% dumber than in real life. (Science fact.)

With that in mind, here are 10 logical fallacies (blogical fallacies? no?) to know and avoid, commonly found in a comment stream near you.

#1: Appeal to Authority

The appeal to authority hinges on a naïve trust that important people always know what they’re doing. You know how when you were a kid, you thought your mom was some kind of magical genius who could fix anything? Then, you grow up and realize they let anyone be a mom.

The appeal to authority fallacy frequently pops up when you criticize an authority figure – for example, a famous writer or a powerful CEO. For example, see this comment on Larry’s post about eBay’s lousy paid search strategy:

Blog Comment Ad Hominem Attack

Just because eBay is a big company with a big marketing budget doesn’t mean that whoever’s in charge of their PPC knows what they’re doing. Big companies – whole empires even! – fail all the time. The history of the world is a catalog of failures. Authority doesn’t equal competence.

#2: Argumentum ad Hominem

A commenter is resorting to an ad hominem attack when he gets personal, otherwise known as “being a dick.” See the examples below. Both – coincidence? I think not – on posts where I was writing about sexism. When I complained about the Google Doodle for International Women’s Day, one friendly commenter accused me of PMS’ing:

Crappy Comment

Then there was the time I “bitched and moaned” about a literary journal that only published men:

Personal Attacks in Blog Comments

The editor of that journal didn’t like my post and didn’t like my forehead either. (I’ve edited some of these comments for language.)

Protip for comment writers: Leave people’s body parts and functions out of your arguments and you look way more credible.

#3: Ignoratio elenchi

Doncha just love Latin? Ignoratio elenchi is otherwise known as the irrelevant conclusion, missing the point. People who “just like to hear themselves talk” (or see their comments in print, as the case may be) are especially prone to the ignoratio elenchi comment that has nothing to do with anything.

An extra-special brand of this is the irrelevant spam comment – years ago I wrote a (highly ironic, of course) post called “How to Start an SEO Business in 3 Ridiculously, Impossibly Easy Steps,” based on a stupid eHow article, and we still get comments from people who obviously haven’t read the post, thanking me for helping them start their SEO business. For example:

Irrelevant Blog Comment

Sigh. (I stripped the link out and published it to make him look silly, natch.)

#4: The Thought-Terminating Cliché

From Robert Jay Lifton’s book on brainwashing and mind control, Thought Reform and the Psychology of Totalism, we get the concept of the “thought-terminating cliché”:

A commonly used phrase, sometimes passing as folk wisdom, used to quell cognitive dissonance. Though the clichéd phrase in and of itself may be valid in certain contexts, its application as a means of dismissing dissent or justifying fallacious logic is what makes it thought-terminating.

In other words, as some Wikipedia editor put it, “end the debate with a cliché—not a point.” “It is what it is” is the ultimate thought-terminating cliché of our time. It adds no value. Don’t engage with commenters who refuse to engage with you.

#5: Appeal to Tradition

The appeal to tradition fallacy, otherwise known as “argumentum ad antiquitam,” insists that we keep doing something simply because it’s the way it has always been done. Tradition, damnit! Popular among commenters who fear change. Used to justify slavery, war crimes, and so forth.

#6: The Just-World Hypothesis

Some people have a tendency to believe, or to want to believe, that the world is fundamentally just and people are fundamentally good. So if you try to point out something evil or unjust in the world, this conflicts with their worldview and they get defensive. “Oh come on, things aren’t that bad!” “Nobody is hurting you on purpose, etc.!” This is also used to rationalize bad things happening – see the tendency for some SEOs to assume that if a site gets delisted or takes a hit in rankings, it must, ergo, have done something bad to deserve this. We can call this the “Just-Google Hypothesis.” But sometimes bad things happen to good people, and it’s entirely possible that a website could get screwed by Google unjustly and for no good reason. “It is what it is,” right?

#7: The Google Effect

More a cognitive bias than a logical fallacy per se, the Google effect refers to the tendency to forget information that can be easily found online. Then there’s the cell phone effect, which leads to people having no idea what their spouse’s actual phone number is. You can see a similar effect in comments when a reader asks a question that either:

  1. Is already answered in the post they are commenting on, i.e., see above, doofus, or
  2. Could be answered with a simple Google search, cutting out the middle man.

This is what the acronym LMGTFY is for.

#8: Fallacy of Composition

Assuming that something true of one part of the whole must be true of the rest. You see this when people say stuff like “But a buddy of mine works at Amazon and he’s real cool so they couldn’t possibly be bad for small businesses!” Similarly, when someone gets burned by a shady “SEO” firm and then goes on to assume that all SEO’s are selling snake oil. Just because part of the “industry” is corrupt doesn’t mean that SEO isn’t a legitimate field.

#9: The Chiller-Than-Thou Fallacy

OK, I made this one up. But I see it ALL THE TIME. Chiller-than-thou commenters are always telling you to relax, get a grip, calm down, be cool, etc. For example, this one directed at my friend Carrie Murphy:

Aggressive Blog Comment

Joke’s on them, because inevitably the chiller-than-thou commenter ends up looking very unchill. I mean, if they’re so calm and relaxed, why are they leaving aggressive comments on your blog instead of just closing the tab and stepping out onto the patio for a smoke? Would a chill person bother to comment at all? I think not.

#10: The Dunning-Kruger Effect

The Dunning-Kruger Effect is the name given to the phenomenon where incompetent people fail to realize they are incompetent because they lack the ability to distinguish between competence and incompetence. That’s part of being incompetent! Put in blog comment terms, the worst blog commenters fail to recognize that they are the worst blog commenters because they’re so bad at blog commenting they can’t distinguish between good comments and bad comments. That’s why they’re always leaving bad comments. This leads us to a troubling conclusion: Some trolls don’t even know they’re trolls. Frightening, isn’t?

Get in on the fun – let me know what logical fallacies you’re tired of seeing in blog comments. Or, just leave a comment with a glaring fallacy of its own, intentionally or unintentionally. That’ll be fun and self-referential!