My guess is that these people are so deeply socialized to be private and anonymous that they simply can’t fathom the idea of a person sticking their necks out to try and do good things for others.
Sure, motivations are never perfectly pure. Humans are complex. But writing people off and tearing them down just because they dare to speak up – I feel strongly against that. It’s a very defeatist, demoralizing attitude, and it makes our society a dull place.
What if we all gave each other the benefit of the doubt instead? Who hurt us so bad that we gotta be so exhaustingly cynical all the time? Everyone, maybe. But surely we can do better.