Ex-NGO employee here: there's a bit of context to add. Depending on the local laws, a one-off donation (especially with a generous but relatively minor sum) might prove more of a burden than anything else; Small but continuous donations are preferred even to comparatively bigger one offs because they allow for better long term planning - even if it means fewer people making donations and less money coming in, from the NGO's POV it's still preferable in the long run; Depending on the context, people going door to door may not even be from the organization raising money, but belong to intermediaries with very specific mandates: sometimes they are contractually bound to ONLY accept continuous donations (or be economically incentivized to do so). TBS, it costs nothing to politely explain verbally those three points (or only the last one, for brevity's sake), and to explain that the sentiment is deeply appreciated even though the donation cannot/should not be accepted, so none of this excuses the rude person OP talked to.