Imagine you have an open house party at your place: Friends bringing friends, and you end up on your sofa with a bunch of guys you barely know, discussing sports or whatever. The people on your sofa might root for different teams, and there might be some friendly banter about the strengths and weaknesses of certain players or what happened in some recent match. But if you are unlucky you get the obnoxious guy, who starts insulting you and your friends for supporting a different team, and whose behavior is becoming increasingly louder and impolite. At some point in time you need to step up, make use of your domestic authority, and kick that guy out from your sofa and your house.

A blog works just the same way. If you have a comments section, you will attract comments from people who disagree with you. If you think a bit about the psychology of that, you'll find that of course people who agree with you will rarely bother to express that, while the stronger somebody disagrees with you, the more likely he becomes to comment. So your comment section will always be biased against the opinion you expressed in your post. And if you try saying something balanced, you'll be attacked from both extremes. And all that is all right, and part of the normal discussion culture of the internet.

But sooner of later you'll get comments from "that guy", the obnoxious one looking for a fight, either with you or with somebody else commenting on your blog. He might be insulting, he might be trolling, he might be trying to derail your thread, and the better your arguments are to prove your point, the more aggressive he will become. And then you need to apply the sofa test: If the guy is behaving in a way where you'd have kicked him from your sofa and your house in real life, you need to kick him out of your comment section of your blog.

Of course that will cause howling about censorship and freedom of speech. But actually it is the aggressive troll who is impeding the freedom of speech of you and your other commenters. Once a comment thread goes down in a blaze of fire, any rational discussion of the subject becomes impossible. Only by imposing certain standards of polite discussion can you maintain a comment section of value.

Oh, and once you got a decent pagerank and popularity, you'll get comments advertising questionable websites and the like, with links, for everything from gold sellers to casinos. Don't think twice, delete those immediately!