The Categorical Imperative is a moral obligation
To act morally is to do one's duty and one's duty is to obey the moral law. Duty is done for its down sake. Doing it for any other reason does not count.
Treating people as means to ends is exploitative. To be consistent, we need to value everyone equally.
A Categorical Imperative can be universalised (ie applied to everyone without exception). A maxim (rule) cannot be universalised if it is contradictory. There are 2 contradictions.
According to Kant , a benevolent act that is motivated by inclination alone lacks moral worth.
1. In Utilitarianism J.S. Mill argues that obligations of justice are more stringent than obligations of benevolence.
C. Obligations of justice are discretionary duties to be fulfilled as one sees fit.