Sexual harassment? Sure. Sexist? Sorry, no, that's just silly. By your logic, if a male manager only propositions female subordinates, it's sexist, because he isn't also propositioning male subordinates. That's not sexist, that's a side effect of the male manager being heterosexual.

By your logic, every person that only dates people of a particular sex is "sexist", which is completely ridiculous.

You're thinking that I label the behavior sexist because the manager propositions only women and not men. I am not. I am labeling the behavior sexist because it contributes to both a work culture, and the wider culture, which excludes women from status and power.

I don't know about this; it isn't completely unheard of for female managers to proposition male subordinates, it just doesn't happen as often obviously. I think it's wrong and abusive, no matter which sex does it (and to whom; (gay) men propositioning other men happens too), but I have a hard time seeing how this is "sexist" or only harmful to women, though obviously, due to inertia I think (more men being in positions of power), it negatively affects women more. I will grant you, however, that it can be argued that it contributes to keeping the gender-unequal status quo.