Everyone does. We judge people by their intentions and character all the time, not by the goodness of their actions.
Take Bill Gates. He has done a tremendous amount of good. But he does it in a low-key sort of way, because he really does not care about what the public thinks. He has a huge amount of capital and just goes about doing his business, improving the welfare of some of the worst of people on this planet. His public appearances are mostly to further this cause.
He is ignored. he would not come to mind when people think of someone who has helped and been nice. Instead, it's some celebrity who posted on instagram how hey helped someone. The good they did is almost negligible, and they did it not because they wanted to do good (if they did, they'd do different things), they did it to capture the hearts of their retarded fans.
To those of us not completely naive, the selfishness and manipulation that motivates such actions exceeds the little good (helping one homeless person with, say, MMA gloves? wow, that's gonna make a difference!). they do and we are left with a bad taste.