Appeal to Inherent Nature

A subset of Appeal to Nature; if something is naturally predisposed to a certain act or state, it must be accepted. Snakes bite, bears maul, poisons kill, babies scream, sociopaths torture, and Nazis commit genocide; but those are their natures, so we should not hold it against them. The fallacy is, of course, that the people making this claim are conflating inanimate objects, animals, and people. One of the three things I just listed has moral agency (i.e., the capacity to make value judgements based on an abstract idea of right vs. wrong and to be held accountable for those choices), and the other two don't. Guess which one.

Used as one of the Jerk Justifications. For when a man is appealing to his perverted nature, see I'm a Man, I Can't Help It.

Examples of Appeal to Inherent Nature include:

Comic Books

In issue #3 of IDW's Godzilla: Kingdom of Monsters series, the No Celebrities Were Harmed version of Lady Gaga said that humanity shouldn't hold it against giant monsters for rampaging and destroying cities; it's just what they do, and it would be wrong to kill them for it.

Film

Natural Born Killers provides an alternate rendition of the below entry:

Once upon a time, a woman was picking up firewood. She came upon a poisonous snake frozen in the snow. She took the snake home and nursed it back to health. One day the snake bit her on the cheek. As she lay dying, she asked the snake, "Why have you done this to me?" And the snake answered, "Look, bitch, you knew I was a snake."

Folklore and Mythology

In the form of The Tale of the Scorpion and the Turtle, it dates back to an ancient Sanskrit collection of folklore that was first translated into English in 1570.

A scorpion, being a very poor swimmer, asked a turtle to carry him on his back across a river. "Are you mad?" exclaimed the turtle. "You'll sting me while I'm swimming and I'll drown."
"My dear turtle," laughed the scorpion, "if I were to sting you, you would drown and I would go down with you. Now where is the sense in that?"
"You're right!" cried the turtle. "Hop on!" The scorpion climbed aboard and halfway across the river gave the turtle a mighty sting. As they both sank to the bottom, the turtle resignedly said, "Do you mind if I ask you something? You said there'd be no sense in your stinging me. Why did you do it?"
"It has nothing to do with sense," the drowning scorpion sadly replied. "It's just my nature to sting."

- This trope does get a twist in Legend of the Five Rings, however, as Shinsei the sage tells Bayushi of the Scorpion clan a version with a different ending (it also used a frog rather than a turtle): "Little frog, I can swim."
A similar tale about a jackal and a camel uses this trope twice. The jackal wants to get at some tasty crabs on the other side of the river, but he's not a strong enough swimmer to beat the current. A camel comes along to get at the sugarcane that's also across the river, and agrees to ferry the jackal across. So the jackal eats his fill, but being much smaller than the camel he finishes before the camel has a chance to get more than a couple of mouthfuls; and, being full and happy, he prances about, yipping at the top of his jackal lungs, alerting the farmers to his presence and that of the camel. As the camel is swimming back across, he demands, "What the hell was that?!" "Sorry," says the jackal, "when I'm full I just feel like dancing around and yapping. It's just how I am." So the camel starts rolling over and over in the river. "What are you doing?!" cries the jackal. "Oh, sorry," says the camel, "But whenever I finish eating something I just feel like rolling over and over and over. It's just how I am."

Literature

In Jingo, "71-hour Ahmed" points out that if this is a valid excuse for people to do bad things, then it's an equally valid excuse for those with a sense of justice to punish them:

Oh, no doubt the man would suggest there were mitigating circumstances, that he had an unhappy childhood or was driven by Compulsive Well-Poisoning Disorder. But I have a compulsion to behead cowardly murderers.

Live-Action TV

In a crossover between media and real life, this fallacy often shows up on reality shows, with at least one contestant each season declaring proudly "That's just who I am." when called out for acting like a bigot, an asshat, or a bitch.
When Aeryn in Farscape says that John Crichton is obsessed with sex, he says, "I'm a guy!"
In the ITV series Primeval, a character who has been raising an orphaned sabretooth since it was a cub insists that the now fully grown cat would never attack her. Which, naturally, it does.
Summarized quite nicely in Star Trek: Deep Space Nine by the 217th Rule of Acquisition: "You can't free a fish from water."
Mary in Downton Abbey, who argues that she's inherently contrary and that it would be against her character to want to marry anyone who anyone else wanted her to marry.

Tabletop Games

One of the most universally despised yet virtually ubiquitous excuses for bad behavior in role-playing games is "I'm just doing what my character would do" (and its little brother "I'm just acting my alignment"). As if once one has written "Chaotic Neutral" on his character sheet (through no fault of his own, presumably), it would be a sin against role-playing not to do something random, disruptive, and, if possible, stupid every now and then. Because that's what Chaotic Neutral people do! And it's not just players - more than one party has been betrayed and attacked by an NPC they were currently in the process of helping simply because the GM noticed its race's alignment was evil, and why would an evil person pass up an opportunity to do something nasty?
- The most infamous example would have to be the Paladin class in Dungeons and Dragons, holy warriors who were required to be Lawful Good. So many players - many of whom were perfectly capable of playing non-paladin Lawful Good characters as reasonable individuals - felt that the only acceptable characterization for a paladin was the aggressively evangelistic Knight Templar whose only possible reaction to any situation was to demand everyone share his beliefs and kill anyone who didn't immediately fall in line that the phrase "Lawful Stupid" was coined to describe the class as a whole. The 4th Edition of D&D removed the alignment restriction, but many players familiar with earlier editions still act that way, because "that's just how paladins are."

Real Life

Often used by people who want to excuse their own bad behavior rather than admit that maybe they crossed a line somewhere. "It's just the way I am." Not a 100% fallacious argument in that it's got some basis in fact when taken on the level of a single person, but fallacious enough that it usually comes off as lame and immature when people use it.
- This has often come up in discussions on bullying. People who see bullying as being "no big deal" (and believe that the victims need to "toughen up") will often invoke this fallacy, along with Appeal to Tradition.
Often used to imply that the person objecting to the behavior is prejudiced or overly sensitive.
This is also a trope in certain religious/spiritual teachings, where it is assumed that value is subjective and not inherent to the thing in question.
Often combined with Moral Myopia. "It is my tribe's natural custom to conquer and enslave and plunder therefore you are unjustly interfering with our culture." Of course it is every tribe's natural custom to conquer and enslave and plunder. And if a stronger tribe happens to have a hankering for expressing that desire by stopping you, who the heck are you to complain? They are just following their natural custom.