That interpretation seems more like your own opinion rather than the opinion of those who actually say that. I see little causal relevance between charity and trickle down economics.

You have to think more impartially to understand why these two train of thoughts have little to no intersection. Do you know why these people you're characterizing are saying "people are generous"? Because like you said, greed is simultaneously said. If you get it, you'll see it's not about trickle down.

Additionally the general right wing argument for the structuring society around volunteer charity over forced social care is that volunteer format is enough from the view of the giver, not that they will get enough from the view of the receiver. If that happens to be nothing, they're saying so be it. If that happens to be a lot, that's great. The argument is also about having the option to choose where they help rather than a government body choosing it... Though I don't think individuals could possibly know though to choose well.

I am not making an argument for the right or left. I'm just fixing the polarized viewpoint of the other party.