If you think that the appropriate answer to "women feel scared to reject men because of common toxic behavior" is "but its not all men"... I'm sorry to call you out but you're part of the problem.
Instead of being defensive, try to see it from their point of view and accept that something is messed up where a lot of men are like this. And I don't agree that women that are rejected react like this. Quite the opposite actually.
It's an undeniable reality that women get unsolicited advances from men multiple times a day, whereas the opposite is not true.
Maybe I'm misunderstanding then.
My interpretation of the comic is that the woman's first instinct was to feign interest to prevent any toxic behavior being directed to her. Then the man told her to disregard that and simply reject him which she does, then her instinct is proven right.
That to me signifies that she did not feel safe to reject him.
The way I understood your argument is that this fear of rejecting a man from panel 1, or assuming a bad reaction is "sexist" because "Men are not a monolith". I'm not sure this is appropriate to the point the comic is trying to make.