I'm not sure why it matters if they're "a sexist".
Whether they make a decision based on internal biases caused by societal norms, or make a decision by measuring those societal norms directly and responding to them, the decision is still an expression of societal sexism.
Whether they make a decision based on internal biases caused by societal norms, or make a decision by measuring those societal norms directly and responding to them, the decision is still an expression of societal sexism.