A sweeping generalization. It's sweeping right now! Can't you see it? Look! It's sweeping over there!
I have a problem with this idea (I have heard it in many, many other places besides here) because it tried to pass itself off as the end-all be-all of stimulation. It would be more accurate, in my opinion, to say that "Women are more apt to be turned in verbally, and men more apt to be turned on visually."
But has anyone tried to reason this out? My personal belief behind it is that, while wen are more likely to get 'turned on' by visual stimuli, it's because of social conditioning versus actual physiology. I can't tell you how it began, because I don't know, but it probably happened many generations ago.
Women, until recently, have been taught to repress their sexuallity as much as possible. Therefore, it is not 'right' for a women to be tittilated by visual stimuli lest she be labeled a jezebel, for she is focusing on the 'carnal' and physical side of the issue.
Men, OTOH, are taught to repress their sensuallity. They (we) are conditioned to separate the physical acts from the emotional and mental corralaries.
This is not to say that things can't change. I'm not female (at the moment), but I'm damn sure there have been women to have snuck a peek at their husband in the shower and it got their blood pumping. And, to go with it, I know from personal experience that spoken and written words can be an aphrodisiac.
The 'problem' here is not that we are not excited by certain things, but that we refuse to let ourselves be excited by them.