In the time that I was a regular reader of Slashdot, I saw a few exchanges that stayed in my mind. I later went back to find them, but was never able to. So that they're not lost to time, I figured I'd post all the ones I remember. What follows is from memory, and prettied up a bit. (Not trying to plagiarize, if you can find the original post for any of these, let me know.)
[Story: Armadillo Aerospace has a failed rocket launch.]
A: Well, I think we can close the books on Carmack's little project.
B: Come on, now. Private space travel is still in its infancy. There are growing pains. Not everything works the first time. But what's important, is that we're learning from these events. Armadillo is learning. They'll adapt. And the next voyage will be better and safer!
C: You mean, even safer than a big orange fireball?
A: [long rant] So that's the problem with this ban on incandescent light bulbs.
B: Whoa whoa whoa, slow down. There is no "ban" on incandescent light bulbs. It's just that the government passed new efficiency standards, and incandescents don't meet them.
C: Oh, that's clever! I should try that some time: "See, I'm not breaking up with you! I'm just raising my standards to the point where you no longer qualify."
[Story: a pedophile was caught because he took pictures of his acts and tried to blur out the victims' faces, but police analysts were able to unblur them.]
A: Hah! What an amateur! Everyone knows you have to do a true Gaussian blur to destroy the information content of the picture!
B: Yeah, or entropize it by blacking out the whole face.
C: Right. Or, you know, you could just ... not molest children.
(IIRC, C was heavily voted down and criticized for assuming guilt.)
[Story: police used "big data" analytics techniques and discovered that most robberies occur on paydays near check-cashing places, which allowed them to ramp up arrests.]
A: I don't know, this seems kind of big-brothery...
B: Not at all! This is the kind of police work we should applaud! Working only off publicly available, non-private data, they found real, actionable correlations. It wasn't just some bigoted cop working off his gut: "Oh, this must be where the thugs go ..." No, they based it on real data. What's more, it let them avoid the trap of guessing the wrong paydays, which can actually vary! Some people get paid weekly, some biweekly, some of the 1st and 15th. For example, I get paid on the 7th and 21st.
C: So, uh ... where do you cash your checks, by chance?