Having worked many years in non-profits, it's sadly an all too common issue. I have a number of explanations for why people are like this toward people who are already giving more in a month than the critic will give in a lifetime, ranging from a kind of need to belittle the giver's generosity - to quell the critic's own discomfort at the fact that they may not be as generous a person as they would like to think, through to many people taking generosity as a sign of weakness and exploitability - and thereby somebody who can be bullied to let off a bit of steam.

It's exhausting though. The giver ends up in this awful moral quandary where all they want to do is throw their hands up and say "eff-this and eff-all-of-you", but at the same time, this kind of person if the type who can't bring themselves to let the crappiness of others lead them to abandon vulnerable people in need. And so the spiral toward burnout spins down and down.