It is the donating 20% that measures (in part) my ethical standard
You seem to be somewhat contradicting yourself. You’re criticizing others for equating sacrifice with virtue, but then measuring virtue as the percentage that you sacrifice! What matters is how much you help people. If you donate $3,500 to buy bed-nets, you’ve (in expectation) saved a life. It doesn’t matter whether that was 10% of your income or 1% or 0.1%. The important thing isn’t the percentage donated, it is the total amount donated. By asking someone earning less than you to donate 20% (or whatever it is you donate), you are asking them to do less good than you do. To be asking the same of them as you do of yourself, you would have to ask they donate a higher percentage, or increase their income.
You seem to be somewhat contradicting yourself. You’re criticizing others for equating sacrifice with virtue, but then measuring virtue as the percentage that you sacrifice! What matters is how much you help people. If you donate $3,500 to buy bed-nets, you’ve (in expectation) saved a life. It doesn’t matter whether that was 10% of your income or 1% or 0.1%. The important thing isn’t the percentage donated, it is the total amount donated. By asking someone earning less than you to donate 20% (or whatever it is you donate), you are asking them to do less good than you do. To be asking the same of them as you do of yourself, you would have to ask they donate a higher percentage, or increase their income.