The idiom isn't gendered, a component of it is. Likening someone to 'the little dutch boy with his finger in the dyke' makes no claim on the gender status of the referent and is equally applicable across all genders. If they insisted on calling you Mr. Egon, then sure, that's misgendering, but 'go off king' is a established turn of phrase that I have also seen generically applied because it likewise makes no claim to the gender status of the individual referred.