I can't speak for tptacek, but I feel like the term "white knight" is incredibly misused, and 9 times out of 10 (including the way it was used in the current comment thread) it needs to die.
The reason is simple: Like all ad hominems it's a way of opting out of engaging with a speaker and their arguments. Rather than saying "Well, you're wrong because of X, Y, and Z" you say "you're just white knighting", and suddenly there's no need to list out any arguments.
Even beyond that, the entire logic framework behind the term is itself toxic; it's rests on the unspoken assumption that arguments are only as valid as the intentions behind them. I know nothing about the WMF's HR policies, nor do I have an opinion on whether Stierch should or should not have been fired. But if I say "she should not have been fired because other employees in the same situation have not been in the past, and this creates a double standard" (which as far as I know is not actually true; this is a hypothetical), it doesn't matter if I'm saying it because I like Steich as a friend, or I want to sleep with her, or I behave like that towards all women, or I got into a fistfight with someone from the WMF in a bar once and have a grudge against the whole group; either my assertion is right or it's wrong. A facile accusation that I'm only saying that because I want to sleep with her (which is what the "white knighting" term means in this context) could be true, and it just wouldn't matter.
In short, the term "white knight" is employed, almost without fail, in an attempt to bully and shut debate down; as the crudest of ad hominems. And it needs to die.
(Edit: For the record, I truly have no opinion on Stierch or the WMF in this case, and I haven't even bothered to look at the comments being discussed. This is nothing to do with this specific case.)
The reason is simple: Like all ad hominems it's a way of opting out of engaging with a speaker and their arguments. Rather than saying "Well, you're wrong because of X, Y, and Z" you say "you're just white knighting", and suddenly there's no need to list out any arguments.
Even beyond that, the entire logic framework behind the term is itself toxic; it's rests on the unspoken assumption that arguments are only as valid as the intentions behind them. I know nothing about the WMF's HR policies, nor do I have an opinion on whether Stierch should or should not have been fired. But if I say "she should not have been fired because other employees in the same situation have not been in the past, and this creates a double standard" (which as far as I know is not actually true; this is a hypothetical), it doesn't matter if I'm saying it because I like Steich as a friend, or I want to sleep with her, or I behave like that towards all women, or I got into a fistfight with someone from the WMF in a bar once and have a grudge against the whole group; either my assertion is right or it's wrong. A facile accusation that I'm only saying that because I want to sleep with her (which is what the "white knighting" term means in this context) could be true, and it just wouldn't matter.
In short, the term "white knight" is employed, almost without fail, in an attempt to bully and shut debate down; as the crudest of ad hominems. And it needs to die.
(Edit: For the record, I truly have no opinion on Stierch or the WMF in this case, and I haven't even bothered to look at the comments being discussed. This is nothing to do with this specific case.)