I also didn't get it at first, but I am not a native English speaker. I think it's a play on the phrase "Enhance your penis" that is typical for spam emails trying to sell dubious medication.
I understand that, but I fail to see how it's especially offensive women? I consider it primarily against good taste. ;)
It is not offensive at all (i agree it is bad taste, though i didn't understand the joke).
It is sexism if you understand sexism and genderism in its strictest sense: That there is no difference between man and woman - sex is a thing imposed by society - and mentioning things like the penis, the biological difference between man and woman, constructs that change, thus is sexism.
I understand that, but I fail to see how it's especially offensive women? I consider it primarily against good taste. ;)