A white knight is a "nice guy" obsessed with the idea of coming to a woman's aid. He is typically overprotective of women, takes any minor complaints towards them very personally, and subconsciously believes women can do no wrong.
White knights are often sneaky and manipulative towards females. They may defend females from verbal or physical insults. Not rarely, they will throw other men under the bus only to increase their chance with a woman, or only to appear socially favorable. White knights are very convinced of their moral superiority, typically motivated by feminism and, unwittingly, by their sexual frustration.
Both women and men hate white knights. Women hate them because their niceness pressures them into reciprocity, but nice men do not fulfill women's mating preference for the most dominant men available. An exclusively nice man cannot be dominant. Men hate white knights because they inflate women's egos and standards.
The most contradictory occurrence of white knights can be found on anti-incels forums, where the users generally agree that pressuring a woman into sex by being nice is obtrusive, yet the men active in these places appear to largely be doing just that. For this reason, it is thought anti-incel ideology is inherently self-destructive and that most such incel-haters as well as male femininsts are incels themselves.