I have noticed that in discussions between Catholics and secular liberals on the subject of political, social or religious tolerance, the probability of the secular liberal raising the Inquisition is equal to "1".

In fact, it is usually raised in the second or third round of the exchange, just before the the "Giordano Bruno gambit" is deployed. (And check out this post if you are thinking "who the heck is Giordano Bruno?"

I was motivated to diagnose and fix the rules of this tactic - which will henceforth be known as the "Bradley Universal Reductionist Principle", aka the "BURP" - in the lexicon of argumentative techniques because of this post by John Derbyshire at National Review Online:

REDUCTIO AD INQUISITIONEM [John Derbyshire]
Further to Ramesh's point, a couple of readers have reminded me that referring to the Inquisition when writing about religion is like referring the the Nazis in a political discussion. Play stops and everyone goes back to his last legal position. Sorry about that

Sounds like a fair rule - and it will henceforth be known as the "Derbyshire Orthodox Reply Condition" or the "DORC" - particularly since the Inquisition which is used as the argumentative version of a nail filled sock isn't the Inquisition of historical memory, but something deeply metaphorical and legendary. But explaining that distinction in the midst of a discussion requires too much effort because one has to walk uphill against a whole bunch of conventional wisdom.

Incidentally, the use of the Inquisition as a rejoinder in arguments about the modern idea about freedom of conscience is a classic example of the "tu quoque", or "you too", fallacy. Assume, for example, that in response to my argument that prejudice against evangelicals is bad, the response is made that the Catholic Church had a history of burning people who didn't convert to Catholicism. That response would be an example of the tu quoque fallacy since (a) it is an absolutely irrelevant comparison and (b) it is implicitly an ad hominem attack on proponent of the argument, rather than the argument itself. It essentially argues, "don't listen to this guy because people like him are evil or corrupt."

Update: For an example of a "BURP" in progress, check out this comment thread at Moonbat Central, which moves from a discussion of the movie, Kingdom of Heaven, to a tu quoque on the Inquisition in about 10 posts. Then, when the historical facts of the Inquisition are provided to counter the BURP, the original poster "sees and raises" by invoking the Albigensian Crusades and the Thirty Years War, but oddly fails to see the generally show-stopping "Giordano Bruno gambit". He ends with this measured observation:

The Catholic Church is the longest lasting criminal conspiracy in history and I would no more accept the word of the Church than I would accept the word of Sammy "the Bull" Gravano, who, by the way, is a practicing Catholic.

See how the Tu Quoque fallacy works?