Mediation Backfire

"And just like that, all the hatred they had for each other was instantly directed at me."

—JD, Scrubs

Everyone knows when you see two dogs tearing into each other, the last thing you should do is try to get between them. What some don't realise is that the same can be true of people, too.

Two characters in the middle of a bitter argument make up their differences over a common love of abusing someone else - usually, but not always, the person who tries to get them to make up in the first place. They'll tend to start out with grudging Dumbass Has a Point and Actually Pretty Funny's, before really warming to the tag-team beatdown.

Mediation Backfire can cross over with Truth-Telling Session. The Ass in Ambassador often invokes this trope, albeit unintentionally.

Subtrope of No Good Deed Goes Unpunished, and related to Stop Helping Me!. Inversion of Apple of Discord, when a third party makes two allies start arguing - this is about making two arguers temporarily join forces against the intruder. Compare/contrast Enemy Mine, when two mortal enemies join forces to defeat a mutual threat, and Ignored Enemy, when two allies start fighting with each other and ignore their mutual enemy, who tries to get them to focus on him again.

Examples of Mediation Backfire include:

Anime and Manga

As Revy and Roberta are beating the nine hells out of each other in Black Lagoon, Rock gets the bright idea to try to get them to talk about their problems. Being as both of them are in full-on violent mode, the response from the two is unsurprising:

Revy and Roberta: (simultaneously) STAY THE FUCK OUT OF THIS!

Ranma ½: When Gosunkugi gets ahold of paper dolls capable of controlling anyone he wishes, he tries to use this opportunity to win Akane's heart. Unfortunately, after he test-drives a few of his dolls on Ranma to see if they actually work, Ranma's suspicions are raised to the point where he openly confronts him about it. Akane immediately rushes to Gosunkugi's defence and our two opposing sides begin to bicker.

Ranma: How come you're bein' so stupid, stupid?!
Akane: Speaking of stupid, look in a mirror!
Gosunkugi: Um, Akane? Ranma? Please calm down. I haven't put the doll on, so can you not fight until I-
*both Ranma and Akane send him airborne*
Ranma: You stay outta this!
Akane: This is between me and Ranma!

In the Azumanga Daioh comic strip, Sakaki once sees two cats about to fight. She instantly rushes in to stop them, but since the affection is pretty much one-sided on Sakaki's part, they both settle for chomping her hands instead.
This is a pretty common fate for anyone who steps in between Ryoko and Ayeka in any version of Tenchi Muyo! The biggest one comes towards Tsunami, who finds her explanation about herself and Sasami interrupted because the two are more worried that Tsunami is gonna be Sasami in the future and when she tries to get their attention, they both tell her to shut up!

Literature

In the Robert Asprin book The Sweet Myth-tery of Life, Guido describes this as an inevitable result of getting involved in a domestic dispute.
- As previously shown by Skeeve in Hit or Myth, when he got the reluctantly married king and queen to get along by telling off both of them.
Very deliberately Invoked Trope by Saki in "Excepting Mrs. Pentherby".
In Dresden Files, Harry tries to defuse what's about to go down between Ebenezer McCoy and Jaren Kincaid. He ends up with a gun pointed at his face and his spine.
Discussed and defied by the Feegles in I Shall Wear Midnight - "Any man who interferes with the arguin' of women is gonnae find himself with both of them jumpin' up and doon on him in a matter of seconds".

Live-Action TV

In Black Books, Bernard and Mannie take time out from an argument to insult Fran, and end up resolving their own differences in the process.
- Until Fran leaves the room.
From Scrubs after JD intervenes in an argument between Dr. Cox and Jordan;

JD: And just like that all the hatred they had for each other was instantly directed at me.

In the Xena: Warrior Princess episode "Been There, Done That", Joxer attempts to invoke this trope in order to stop the feuding families. He gets a couple dozen arrows to his face for his trouble (but again, this being a Groundhog Day Loop, he gets better).
Played with on Frasier; Frasier sits Roz and Julia down in the cafe to try to get them to make nice, and when they find common ground insulting him, he graciously leaves them to it. The moment he's gone, though, they both get up to leave, and are bickering again before they reach the door.

Theatre

This trope, along with The Masochism Tango, is the entire point of the Edward Albee play Who's Afraid Of Virginia Woolf. George and Martha attack each other at every turn, but take more delight in ganging up to tear apart the innocent young couple they invite round for drinks, (lots and lots of drinks). It's heavily implied they do this all the time to keep them from killing each other.

Web Original

Flame Warriors' typically verbose description of forum users has this to say about the archetype they call Diplomat:

Diplomat butts into hot disputes, presuming that the combatants will welcome and appreciate his even-handed and eminently reasonable mediation. Frankly, he gets what he deserves.

Invoked by ED-tan in this user-created Gaia Online comic episode.

Western Animation

In Family Guy, Peter is upset that he can't find way to bond with Stewie, until he discovers that beating up Lois is the perfect way to do it. Crosses the Line Twice when they lock her in the trunk of a car and sink it in a lake.
On The Simpsons when Marge went after Itchy and Scratchy, the series staff did an episode where a squirrel character based on Marge tries to stop a fight, but the duo decides to knock her head off instead. Given that the only other time they've worked together against someone else was an old wartime special where they beat up Hitler...