Paul Graham, noted programmer and programming textbook author turned venture capitalist, has some ideas about how we ought to disagree. It became pretty obvious we think about disagreements differently, as I read through that, but it certainly sounds very persuasive, so let me talk about one specific issue I have: ad hominem attacks are actually better discourse than responding to tone.
The example he gives as 'responding to tone' is: "I can't believe the author dismisses intelligent design in such a cavalier fashion." This is an extremely insubstantial critique. I think Graham would agree – it raises a problem with the perceived internal methodology of their conversation partner. 'I think you're thinking about this in a sloppy way' it says – and I think his example is close to the best possible use of it. Most of the time, this category consists of e.g. calling someone hysterical. It's an old family joke, that the one way to massively piss someone off is to tell them to calm down. It's condescending, dismissive, and prevents them from using even very appropriate and metered emphasis. They make a single exclamation, and they're shrill – and the condescending person deems themselves fit to judge them.
Concerns about tone are hard to get right. They require empathy, of course – you are essentially trying to read someone's mind. But our own etiquette requires we do not use people feelings as weird weapons against them. It's better we state things plainly, and not worry about concealing ourselves. To criticize someone's tone, or any other element of their emotion, risks teaching them to hide their feelings from you. If you want to build trust, and really communicate, you ought not do that.
Of course, third party ad hominem attacks are way better. They're practically slam dunks, even though it extends the conversation past the bounds of Platonic debate. Alex Jones is a complete nutbar. That should be enough to wave off a well meaning friend. We live in a society where trust is real, and we shouldn't be afraid of weighing it. You shouldn't trust a senator about some bill that expands their power. No society built on trust should even get to the point where that's a reasonable thing to demand. If there are no impartial defenders, it can be dismissed instantly – and should be. I'm sure Paul Graham keeps busy, refuting the central thesis of all the scammers and dillweeds that he bumps into. But for everyone else, we know who we trust, and that trust is built slowly.
Of course, if you're talking to that senator, the etiquette gets a little tricky. It will be a bumpy road if you tell someone you can't trust them because of their job title, for instance. But, if you are careful, you can give people a chance to explain why their idea is good. Give people a small chance to build trust. Be honest about your skepticism, and open to the chance they're being forthright. Even direct ad hominems can be used to build trust on previously shaky ground.
Of course, I'm not sure how Graham would react to this. Am I just contradicting him (level 3) or am I making a counterargument (level 4). I think we'd both agree that I'm not refuting his central point (level 6), because his focus is so split in that essay he might not have a central point. Is the swapping of those two items central enough to be even possibly convincing (because, for those that haven't read his work, he dismisses everything below a certain, unspecified, level). Or is an appeal to etiquette and good faith conversation just gibberish in his eyes?