Never take advice from someone who thinks it's meaningful to talk in terms of "what women want", as if there's this undifferentiated mass with a unanimous set of values.Never underestimate the power of generalization. Women are shorter than men. Women are slower than men. Women are physically weaker than men. These generalizations allow for individual exceptions, of course, but they are true in an important statistical sense. They allow us to predict that, for example, most top basketball players, powerlifters, and sprinters will be men. Indeed, it's no coincidence that the recently completed Olympics had separate competitions not only for physically disabled athletes (the Paralympics), but also for women. They could not in general compete otherwise.
Returning to your point, I doubt you really believe that it's meaningless to talk in terms of "what women want".
Despite variation in individual tastes, in general women are attracted to charming, confident men. Moreover, I'm sure you could add a few more adjectives to that list. QED.
How about if we correct that to: "when the girl responds positively to the guy, and he keeps going, it's flirting, but when she responds negatively (or tries to avoid him) and he keeps going anyway, it's creepy/sexual harassment".
I wish you were right. Much of the time, men have no slack in this regard—in today's hypersensitive environment, it's often "one strike and you're out". The costs of being accused of sexual harassment are high, while the costs of making false accusations are low; this leads to predictable results.