Tone argument

Person A: [bigoted statement] Person B: The fuck? Person C: Now, now, let's have civility. Dear C: You came in one statement too late.

I have three things I'd like to say today. First, while you were sleeping last night, 30,000 kids died of starvation or diseases related to malnutrition. Second, most of you don't give a shit. What's worse is that you're more upset with the fact that I said shit than the fact that 30,000 kids died last night.

i regret to inform you, that by resorting to Swear language, you have forfeit this debate. Farewell my bitch

The tone argument (also tone policing) is a logical fallacy that occurs when an argument is dismissed or accepted on its presentation: typically perceived crassness, hysteria or anger. Tone arguments are generally used by tone trolls (especially concern trolls) as a method of positioning oneself as a Very Serious Person.

The fallacy relies on style over substance. It is an ad hominem attack, and thus an informal fallacy.

Forms
A variant is, rather than criticising some irrelevant aspect of your opposer's style of argument, you instead praise them for their politeness or nice penmanship, for their good command of the English language so different from those nasty rappers with all their swearing, etc. In either case you have effectively deflected attention from subject to style and enhanced your own status as an arbiter of taste and value.

Examples

 * Dismissing or refusing to address an objective argument (e.g. statistical, scientific) for spurious reasons. The true objection is not to the tone.
 * A reverse tone troll can be used to compare you, the "good" objector, to strawman "bad" objectors. At least you're not like those uppity objectors.
 * A "call for civility". Note that pretty much any objection is susceptible to being tagged "uncivil".
 * "Shrill" or "militant": objecting sufficiently loudly that anyone actually notices, no matter the actual tone or style of the objection. Women are often accused of being "angry" in their tone when an equivalent output from a man would simply be read as "direct" or "forthright".
 * Objection to a particular word in the argument to dismiss the argument and speaker henceforth.
 * Objection to, or dismissal of, grammar or dialect as response to a substantive point.
 * Rich people responding to criticism with "I don't like your tone!"

Appeal to MLK
The "appeal to MLK" occurs when an activist is criticized for (supposedly) failing to act entirely in accordance with the fictionalized saintliness of some activist. Most common is Martin Luther King, Jr., but occasionally Mahatma Gandhi or Cesar Chavez are pulled in. This example particularly fails in that Dr King's was fundamentally a response to tone policers:

Appeals to MLK are also a form of the argument from authority.

Kafkatrapping
Kafkatrapping is the practice of stating that someone defending themselves against an accusation is proof of that accusation; that is, only a racist would have to prove they're not a racist, and only a pedophile would have to prove they're not a pedophile. Since insane people make insane allegations all the time, this is rather a dishonest form of argumentation: If someone accuses you of being a subhuman monster for no reason comprehensible to the rational mind, just ignoring the accusation is not an option.

Exceptions
Aside from the obvious exceptions (e.g. threats of death or violence), it can hypothetically be employed honestly (in response to emotional appeal) — the tone argument is not always incorrect, you catch more flies with honey than vinegar — but it's not a very good argument because it falls to the style over substance fallacy. At best, it may be a way to point out rhetorical dishonesty in a formal debate, but at worst it is simply awarding victory to whoever is affected the least by what is being discussed.

You don't have to listen to someone and may find their tone offputting. Nobody wants an earful of an obnoxious person. In fact, most people simply do not tolerate obnoxious arguments — and will tend to think of any argument they disagree with as obnoxious — no matter how correct they are, which is why politicians go out of their way to avoid this effect. However, while being unhappy with someone's style may be valid, ignoring the content puts you in danger of being seriously incorrect about the world.

Of course, it can be valid to make the tone argument against someone whose argument lacks a claim or evidence in the first place. Angry venting for its own sake can be a healthy expression (can be), but if they forget to actually articulate a point, there's no "substance" being ignored, and all that's left is "style." Sure, they may think their audience knows what they're alluding to, but some or all of the audience may legitimately be baffled about what they're getting at. You can't unilaterally scream obscenities at someone and then call them out as tone policing when they (or your allies) tell you to stop.

There's a difference between criticising someone's tone from a position of power or privilege (e.g. a white person complaining about a black person) and from a position of vulnerability (a black person complaining about a white's tone). Those in power typically have less skin in the game: impolite language will at worst result in mildly hurt feelings. But for those at the bottom, unpleasant tone can produce a culture of oppression and violence: the difference between women joking about raping men and men joking about raping women.

Abuse of the term
If you tread on someone's toes and they tell you to get off, then get off their toes. Don't tell them to "ask nicely".

The phrase "tone trolling" itself can be (and has been ) used to excuse verbally abusing one's opponents, so be careful who you accuse of doing it. Two common responses when it's deployed on you:
 * 1) First, make sure that you are participating in an actual rhetorical debate that both you and your opponent have consented to. Then, make sure that you either have your arguments together or the opponent is not debating in good faith. Bonus points for both, since it can backfire if your own allies contradict you.
 * 2) Light the flamethrowers.

The first of these is probably more productive.