I find a lot of 'white knighting' online at-least, is more about feeling or sounding morally superior, than ACTUALLY wanting to be a constructive change to inspire others. Quite a few vegans fall into this (no shade to vegans, it's literally the first example I knew to pop into my head). They say they want to encourage people to go vegan, but their methods of aggressive name calling and shaming... is just the absolute worst way to get people on your side or inclined to listen.
The way I explain this to people is in an oversimplified way, to hopefully get them to realise why their tactics aren't working:
QUESTION: what is more likely to get people to lower their defenses, and actual open their ears:
a) I understand where you're coming from, but I'd love to talk specifically about a few point I'd disagree with...
b) listen dumb c**t, here's why you're a f**king tw*t...
And yet time and again it's OPTION B the 'white knights' choose to use on-line, which tells you
EVERYTHING you need to know about their true morality and motivation.