As I said in the comment policy, I don't like banning people permanently and will impose lesser sanctions when available. But there are cases where the offense is so egregious, or the bad behavior so persistent, that no lesser sentence will do. In the service of openness and transparency, this is the list of all commenters who have been banned from Daylight Atheism, along with what they did to merit this punishment. I hope it serves as a clear illustration, if any is needed, as to what kind of behaviors I find unacceptable.

Name/Alias: Rev Spitz
Why Banned: Apparently a real person named Donald Spitz, an out-and-out terrorist sympathizer who praises violence and applauds the murder of innocent clinic workers by anti-abortion fanatics. I let his single comment stand as evidence that there are still dangerous lunatics out there, to remind any atheists who might otherwise become complacent.
Offense: Criminality

Name/Alias: Bill Perron
Why Banned: A disgruntled kook with a grudge against James Randi. Claimed that Randi owed him a million dollars because his proposal for a completely unblinded test of astrology was rejected. By itself, that would only have gotten him laughed at. When he started flinging around anti-gay slurs, that was another story.
Offense: Bigotry

Name/Alias: John Donohue
Why Banned: Objectivist drone. Threatened to sue another commenter for criticizing Ayn Rand, pompously announcing, "I have directed authorities to this blog." I do not tolerate threats against me or my commenters, legal or otherwise.
Offense: Threats

Name/Alias: Dutch
Why Banned: A rather strange character with a bizarre and completely idiosyncratic interpretation of Christianity which he wanted to talk about to the exclusion of all else, regardless of the topic of the thread. I put up with it for a while, then it became tiresome. Tried to sneak back under a different name and gave himself away when he couldn't help expounding his weird theology; was promptly banned again.
Offense: Preaching, soapboxing, sockpuppetry

Name/Alias: theistscientist
Why Banned: One of Daylight Atheism's most bizarre kooks. Derailed many threads with semi-literate preaching and Christian spam; I finally had enough and banned him after he left identical comments in six threads calling all atheists mass murderers. When he found out about this, he flew into a psychotic rage and spent an entire night trying, unsuccessfully, to post dozens of raving, obscene, scatological comments. When he realized this wasn't working, he switched tactics and spent some time sending me e-mails in which he threatened to contact every atheist blogger on the internet to expose my duplicity. He promised that my site would cease to exist within several weeks unless I unbanned him. Needless to say, he's still banned and I'm still here.
Offense: Preaching, imperviousness to reason, thread derailing, repetitiveness, sockpuppetry

Name/Alias: wfcxbuldozr
Why Banned: Racist.
Offense: Bigotry

Name/Alias: Christopher
Why Banned: A long-standing commenter who claimed to be an atheist and a nihilist and to recognize no government over himself. When he posted a comment in which he proclaimed himself a "sovereign power" and implied that he would use violence against government agents who came onto his property, I deleted it and warned him in e-mail not to advocate breaking the law on my site again. He chose to disregard that warning, posting another comment which advocated tax evasion.
Offense: Criminality

Name/Alias: imissbubby
Why Banned: Christian troll whose contributions were limited to chanting "Darwinism is a cult" and repeating Christian apologist talking points, even in threads where neither had anything to do with the subject of the post. When I contacted him by e-mail to explain the comment policy, he was hostile and defiant and refused to change his behavior.
Offense: Preaching

Name/Alias: Steve Leone
Why Banned: See this post, plus the subsequent comments.
Offense: Trolling, sockpuppetry

Name/Alias: cl
Why Banned: An initially reasonable-seeming Christian who soon began to overrun every thread he participated in with a steadily greater and greater volume of filibuster-like comments, which invariably boiled down to petty quibblings about wording, grammar or other irrelevancies, or obsessively cataloging all the unfair treatment he felt he'd received from other commenters. When this behavior started driving away other commenters, I restricted him to one comment per day so he could have his say without drowning out everyone else. This resulted in him changing tactics, whining about "censorship" and posting a steady stream of petulant demands that I pay personal attention to him. I ignored this for a while until he finally, deliberately, crossed the line by violating an explicit warning he'd been given about this behavior.
Offense: Trolling