Related to the image of the Knight in Shining Armor on his horse rushing up to protect the poor Damsel in Distress, White Knighting is a common accusation on forums, especially those frequented by a multitude of trolls. In the broadest of terms, it is any attempt to protect or defend a third party on the internet from another's attacks. However, while the attempt may be genuinely meant, it is often seen as Internet Tough Guy posturing, with said defender hoping to look better or earn respect/attention from other forumites. There's an obvious connection here to the way some politicians grandstand over various issues to appeal to the votes of Moral Guardians.
The accusation is most specifically made against male forum-goers who defend female forum-goers, the implication being that they are only doing so because they have a crush on the female in a Double Standard: the kind of Nice Guy that so often mistakes stalking and obsession for love. Though it's most commonly (but not always) a Troll that uses the terminology, like all the most effective insults, it is based on a true observation: forumites do tend to feel a greater need to "protect" females as opposed to males, and all that implies. The trolls using this terminology may also be hoping that the "White Knight" in question will stop defending others, so more people could get trolled with nobody to stop the jerk. You could say that even if the "White Knight" is hoping to get some respect from others, its better than just letting others be bullied. Given that showing other parts of your good side is a socially acceptable way to get the same respect on forums, it can make you wonder why this term has such a negative stigma.
This also happens when someone dares develop their own opinion that differs or even stands contrary to the opinion(s) of the majority on certain issues. When this happen, people immediately leap to the issue or work's defense to slay that heretic by fire. It can also often occur in forums devoted to video or computer games, where if the company or developers of the game are attacked, another forum member will feel the need to come to their defense.
Please note, however, that a person who is being genuinely kind without expecting to curry favor of any kind is not White Knighting (although they will probably be accused of it anyway). Perhaps they have a dash of Chronic Hero Syndrome, but there are some nice people on the internet, after all. Accusing someone of being a White Knight is generally a form of Ad Hominem; the people being criticized cannot attack the argument, so they attack the arguer, whether the accusation is true or not.
- Hisao is (not quite) guilty of this in Katawa Shoujo, particularly in Hanako's route. He's not trying to curry favor, hence the "not quite" part. Hanako is the sort of person everyone wants to protect and hug. This is promptly deconstructed as the arc goes on—in the bad ending to her arc, Hanako snaps at Hisao, declaring that she hates both him and Lilly for "babying" her and thinking that she needs protecting. In the true ending, Hanako lets Hisao have sex with her in order to change his mind about the way he views her. They both realize the mistakes they've been making and the two of them break down in front of each other in the park.
- In Emi's route, she accuses Hisao of doing this, even likening him to a knight on horseback. Hisao's solution in either of the paths to the good ending is to insist that he knows Emi is strong and he is helping her because he loves her.
- Lilly appears to do this with Hanako and (in her route) Hisao, hence Hanako's statement about her in her bad ending. However, she indicates that she is aware of this tendency and tries her best to fix it, and late in her route, tells Hanako that she did not befriend her out of pity, but because she wanted to know more about her, and that she considers her a strong person.
- The term appears in Don't take it personally, babe, it just ain't your story; Taylor makes a post about Kendall breaking up with her girlfriend Charlotte, prompting Akira to accuse Taylor of being a "bitch", which results in Kendall telling him not to be a "white knight" on her behalf.
- Occasionally xkcd is accused of engaging in this kind of behavior, parodied by Chainsawsuit here.
- XKCD's creator Randall Munroe is also accused of this because he argued against Google+'s requirement that member's gender be made public and how this could be losing them users.
- In Homestuck, after Karkat develops a crush on Jade, he flames his own past self for being rude to her. Jade then accuses him, in so many words, of acting like a knight trying to save her.
- Adding to this is that Karkat IS a Knight.
- Entire wikis have been dedicated to how Christian Chandler, creator of Sonichu, attempts to do this in his ever-occurring "Love Quest", and, for that matter, those who try and fail to stop the trolling.
- Captain Hammer from Doctor Horribles Sing Along Blog. Objectively, most of the things he does are morally positive: he fights crime, helps the LAPD stop Dr. Horrible from ruining a bridge dedication, and gets Penny her homeless shelter. However, since he only does it for a combination of personal reputation building and to get in Penny's pants (partly because he likes her, and partly to mess with Doctor Horrible), he is White Knighting incarnate.
- It's not even that he likes her, but rather, he likes the sex.
- Inverted with The Black Knight here.
- The Nostalgia Chick suffers from white knights in her video comment threads and the forums who fail to grasp that her mistreatment of her Sidekick and Butt Monkey Nella is all an act that Nella is completely on board with, and sometimes even writing the script for. Then there are the people on the other side who forget Black Comedy is Lindsay's Author Appeal and try to protect her from the mean guys who are obviously writing everything themselves.
- Gamergate seem to have flushed their population into the open nearly completely. Look up "#AirportsLaw" on twitter. After exploring the first 4-5 pages worth of entries you will see not only the quote of "Airport's Law" itself, but also entirely unsettling amount of examples (the law doesn't mention photo avatars, but they seem to be somehow involved, too) for what on its own would have looked like just a bawdy joke...
- Suggested as an underlying emotional cause of Missing White Woman Syndrome. These kinds of stories strike at white men's desire to protect "their" women.
- This has been used by some armies to justify keeping women out of front-line combat units: trials have shown that male soldiers would sometimes abandon the mission to ensure the safety of female soldiers. Of course, there are many other issues at hand as well.