Money given away doesn't have to have a "noble purpose", the act is good in itself. The people receiving it don't care about motive, I don't care about motive, and the only reason you care about motive is because you're threatened by another person doing good. There's no virtue inherent to giving anonymously. A piece of food or a warm house don't care about the intentions of the original owner of the money.
In fact the only reason I could see for someone pushing a narrative of "only some donations are good because of motive" would be to discourage donations, which I'm not sure why anyone would do unless they are utterly evil.