Taking the points you raise seriatim:
No, I don’t agree this is any particular evidence of my insecurity, or for that matter of my confidence.
No, I didn’t need to be told I was right. I was debating a point. Typically, debate involves the concession by your opposite number of a point he has conceded. Since the point was not conceded, it was still in contention. For this reason, I continued to discuss it.
Yes, I did understand what the thread was about, as all my posts in the thread made clear.
Which is a problem if, hypothetically, you are the one who is wrong.
Bingo. This is it exactly.
And It’s done quite often around here. It slides by way too often because the perpetrator is pushing a position the majority embraces. The game is to be able to use the term both broadly and tightly in the same argument. Thus, a term like “racist” is used to scoop up everyone who might say something merely racial, but the amount of scorn delivered upon the offending party is commensurate with the most vile form of true racism. Rinse and repeat. And when one has the temerity to try to suss out which specific definition is being used, the response is akin to, “What, what’s wrong with you? We all know what we mean!”
The latest case in point, the thread in question.
However, it would seem, to me, that the best counter to this problem would be to provide an example of a Christian claiming persecution in which he clearly did not mean grievous harm.
Dragging in other definitions that muddy the waters does not actually make your point. (Even your appeal to the O.E.D. was lacking in that if one took the various “lesser” meanings of persecution, and cross referenced them to various definitions and usages of persecute, one discovers that persecute went thorough a period of having a separate meaning similar to importune, but that that definition has never been a widely used variant and does not continue today.)
I am also less persuaded by the argument you use, here. It is quite possible that a religious person would use words such as “confess” in ways that are not the common understanding as such words do have separate meanings that amount to religious jargon. It is rather less likely that such a person would use “persecution” in a way that differs from the “common” meaning–particularly when the abstruse meaning is less related to religious discussions.
Oh, hello, Racial.Isn’t.Racist, my old friend, I really didn’t expect to find a shibboleth like you lurking in this thread.
It’s hilarious that a thread about thread derailments is itself being derailed.
Stick to the fucking OP people.
I wish vBulletin gave the OP in each thread moderating powers, so that each thread was moderated not only by the mods of that forum, but also by the OP.
Nope. That would give any poster with a bad attitude the ability to delete posts that he or she did not like or to “edit” posts in ways that would make opponents look bad.
Not going to happen.
Moderator Note
This is ATMB. Dial it back.
I agree that it’s never going to happen on the SDMB, even if vBulletin allowed it, since the SDMB is resistant to change.
Nevertheless, I disagree with the concern that “That would give any poster with a bad attitude the ability to delete posts that he or she did not like or to “edit” posts in ways that would make opponents look bad.”
First of all, the forum mods could ban OP’s that do this. Second, we heard similar concerns about enabling the edit feature (i.e. edit your posts). We heard that bad posters would edit their posts after the fact to make the responses to their posts look bad. As far as I know this never actually happened after post editing was turned on.
I am not sure where you heard objections to the edit function. I have always supported it (with time limits).
You are incorrect that it has not been abused. It may have been more rare (since vBulletin submits a tag noting the editor) and because on the few occasions where it has been abused, the violator was immediately sanctioned.
All that your proposal would do would provide one more area to argue over in ATMB when an OP screwed up and then everyone fought over whether the Mods were correct in their edit of the OP’s edit. We have long said that an OP does not “own” a thread and giving Mod powers would set an appearance of ownership that is not legitimate and that serves no good purpose.
(Is this discussion sticking close enough to the OP?)
See, if the OP had moderating power in this thread, he could delete these posts or move them to the Meta forum 
The new thread has such examples. And they’re very easy to find.
How was this claim not one of grievous harm? I disagree with the author’s perspective, but clearly he considers the phenomena to be more than simply “persistent annoyance”; they are, to him, threatening to his ability to live his life in a religious context.
In any event, pointing to examples such as that would have been a better response than asserting that Fox “persecutes” liberals–a claim that I also find to devalue the word persecute.
And here we have the answer to the OP’s question: " At what point do mods step in when a debate is getting derailed?"
The answer is that they don’t. Because apparently they like taking part in and perpetuating thread derailments themselves.
Or… and I’m just spitballin’, here… or the conclusion is that there was no derailing: the questions raised were utterly germane to the proposition being discussed.
Bricker,
The problem is that using your definition of “persecuted” literally every group of like-minded people in existence are persecuted in some way, shape or form. Christians, Atheists, Right Wingers, Left Wingers, Libertarians, Left Handers, Sports Fans, Geeks … the list goes on. And this is especially true on this board.
That’s what makes your definition so utterly, utterly useless.
I would suggest that if someone starts a thread asking why one of those other groups feels that they are “persecuted”, then a good first step would be to see if it can be established that they feel persecuted using a definition other than Bricker’s.
Or - they could use a standard/common use dictionary to define the word.
*persecute
verb [T] /ˈpɜr·sɪˌkjut/
› to treat people unfairly or cruelly over a period of time because of their race, religion, etc.:
She claimed the government was persecuting its opponents.*
*persecute
verb [T] /ˈpɜː.sɪ.kjuːt/ US /ˈpɝː-/
› to treat someone unfairly or cruelly over a long period of time because of their race, religion, or political beliefs, or to annoy someone by refusing to leave them alone:
Religious minorities were persecuted and massacred during the ten-year regime.
His latest film is about the experience of being persecuted for being gay.
Ever since the news broke about her divorce, she has been persecuted by the tabloid press.*
*per·se·cute [pur-si-kyoot]
verb (used with object), per·se·cut·ed, per·se·cut·ing.
to pursue with harassing or oppressive treatment, especially because of religion, race, or beliefs; harass persistently.
to annoy or trouble persistently.*
*per·se·cute transitive verb \ˈpər-si-ˌkyüt\
: to treat (someone) cruelly or unfairly especially because of race or religious or political beliefs
: to constantly annoy or bother (someone)
per·se·cut·edper·se·cut·ing
Full Definition of PERSECUTE
1: to harass or punish in a manner designed to injure, grieve, or afflict; specifically : to cause to suffer because of belief
2: to annoy with persistent or urgent approaches (as attacks, pleas, or importunities) : pester*
Persecution is the systematic mistreatment of an individual or group by another individual or group. The most common forms are religious persecution, ethnic persecution and political persecution, though there is naturally some overlap between these terms. The inflicting of suffering, harassment, isolation, imprisonment, fear, or pain are all factors that may establish persecution. Even so, not all suffering will necessarily establish persecution. The suffering experienced by the victim must be sufficiently severe. The threshold level of severity has been a source of much debate.
Or not.
You can spitball all you want, but your discussion about whether that particular thread was derailed or not is not germane to the question “At what point do mods step in when a debate is getting derailed?”
And you can see that the first Mod responses to this thread (twickster in post #2 “In general, mods step in when they are made aware that there’s a hijack underway.”, and Jonathan Chance in post #6 “Derailing a thread is a difficult line to moderate…”) are in the spirit of discussing the general question of Mod actions to control derailments, so clearly that was the main thrust of the question in the OP. It clearly was not about whether that one thread was indeed derailed, and it surely was not about what the definition of “persecuted” is.
What’s going on in this thread is clearly a derailment. And having post #59 above by doorhinge, which is a huge dump of the definition of “persecute” is, is a prime example of how far from the question in the OP this thread has gone.