Jonny Fairplay's Grandmother Lie, Survivor
Before Russell, Jonny was one of the most notorious Survivor contestants of all time because he concocted a scheme (pre-filming) in which his friend would come on the show and tell the other castaways that by Jonny's beloved grandmother had passed away recently -- all in a bid to gain Jonny some much-needed sympathy. And in the short run, it totally worked.d
Unacceptable? Well, we're not his grandmother, so we can't hate him too much, but he did also poop in someone's bed on Kill Reality, so let's just say he's a disgusting human being in general.

Stephen and Irene Fight, The Real World: Seattle
Irene was leaving the house for good because of her health, and because she hated it there, but decided to burn bridges on the way out by announcing that Stephen was gay. He in turn followed her out of the house and slapped her straight across the face as she got in a car, then threw her favorite stuffed animal in the bay.
Unacceptable? Yes. At the time this aired, it was the slap heard round the world, or at least the reality world, and it's still pretty shocking since it was totally immature and uncalled for.

Speidi Spread Sex Tape Rumors, The Hills
Spencer solidified his bad boy status by leaking gossip that good girl Lauren Conrad had made a sex tape with her ex-boyfriend Jason. Spencer's girlfriend Heidi was right behind him supporting his lies.
Unacceptable? No. It's annoying, a jerky move and forever ruined the Heidi/Lauren relationship, but the rumors didn't really damage LC's reputation or career.

Justin Plays With Knives, Big Brother
After a bit of standard gay-bashing and other verbal assaults, BB2's bad boy Justin took it way over the line when he got drunk one night and held a knife to the throat of houseguest Krista and then asked her if she'd mind if he killed her.
Unacceptable? Yes. No matter how drunk he was, no one should ever put a knife to someone else's throat, and BB producers made the right call in removing him from the house.

Teresa's Table Flip-Out, Real Housewives of New Jersey
This infamous dinner party was the culmination of a season full of battles and lies, and after a bunch of mud-slinging across a table on everyone's part about Danielle and "the book," Teresa got so angry that she called Danielle a "prostitution whore" and overturned a table.
Unacceptable? Sort of. It was not proper for a grown woman to behave that way, especially when there were children in the room, but those particular teens had seen worse from their own mother.

Screech vs. Sergeant Harvey Shouting Match, Celebrity Fit Club
Clearly Dustin "Screech" Diamond wasn't into being on this show. The former Saved By the Bell star generally liked to stir up trouble and make everyone pretty miserable with his antagonistic remarks. His bad behavior culminated in a confrontation with tough-guy trainer Sgt. Harvey Walden, but they never came to blows. Close, though.
Unacceptable? No. He might have shattered our childhood image of him, and was completely idiotic for trying to goad a fit former military man into a brawl, but it wasn't totally unacceptable.

Marcel's Head Shaving, Top Chef
We always like to think of Top Chef as a classy show that is above all of these ridiculous altercations, but apparently no one is immune to the power of alcohol. Cliff, and some other tipsy Top Chef fellas thought it would be fun to shave the head of annoying Marcel, with Cliff as the one who actually held his fellow contestant down to be sheared.
Unacceptable? Yes. No matter how annoying someone is, juvenile pranks gone wrong are verboten on reality TV.

Margie, Luke, Kisha and Jen Confrontation, The Amazing Race
When there's fighting on this show, it's usually in-team verbal brawls, not physical screaming matches. However, when Jen ran into Luke at a clue box and called him a "bitch," it started a downward spiral of more shoving and more shouting. The battle culminated at the pit-stop mat, when Kisha's giggles caused Margie to start accusing them of being rude to her son because he was deaf, and then making some offensive remarks.
Unacceptable? No. Aside from a shoves and some elbows and some overreacting on everyone's part, it was primarily just a case of poor sportsmanship.

Sharon and Megan's Water Fight, Charm School
We don't expect much from the ladies of Rock of Love: Charm School since the standards there are pretty low, but we do think of Sharon Osbourne as being a little bit better than that. However, during the reunion special, the headmistress was unimpressed by Megan's assertions that Sharon was only famous for screwing Ozzy. Sharon responded by dumping a glass of water on her and then all hell broke loose.
Unacceptable? No. Though Megan did sue Sharon for allegedly pulling out a piece of her hair weave, we can't really blame Sharon for flipping out on the obnoxious bikini-clad reality whore.

Joan and Melissa's Tirade, Celebrity Apprentice
After Melissa Rivers was fired by Donald Trump, she and her mother wigged out on their fellow contestants. Missy even called some of them "Whore pit vipers." Then they stormed out, screaming all the way along.
Unacceptable? No. They were certainly annoying, and completely unprofessional, but the really offensive thing is that while Joan stormed out, she still won the competition.

Amber's Beat-Down, The Bad Girls Club
Again, another situation in which there is too much alcohol involved, as a trip to Cancun turned into a nightmare for Amber M, who got into a hair-pulling tussle with Whitney outside a nightclub. That wasn't so bad, but then Whitney's pals jumped in to help her and started kicking Amber (in the head!) after she'd fallen down on the ground.
Unacceptable? Probably. The show is called The Bad Girls Club, so this isn't too surprising, but to have a group outnumber one person and attack them was really over-the-top.

CT vs, Adam, The Duel 2
Usually when fights break out, it's towards the end of the season when everyone is at their breaking point, CT and Adam came to blows even before the first competition on Real World/Road Rules Challenge: The Duel 2, with both getting ejected from the game. What spurred this battle? Apparently, CT slept with someone new (on the first night there) and his ex Diem called him on it, so he punched the first person he thought might have spread the rumors (unlucky Adam). The two continued to beat the hell out of each other until the rest of the houseguests were finally able to restrain CT.
Unacceptable? Yes. CT has definite anger management problems (he punched a cactus on a previous season), and he also wore footie pajamas to a fist-fight. That's just bad form.