If you think high earners have a morally obligation to give up their income, via tax or whatever, to help the poor in society, then you should also be doing whatever you can to become a high earner in order to contribute in the way you think is right. The logic is this. Those who can help others have an obligation to do so. Therefore if you can help by becoming a high earner, you are failing in your obligation to help others if you do not choose to do so.

By this logic, an intelligent person who chooses to be a writer rather than an accountant is failing in their moral duty to provide for others.