If you worked in a "traditional" corporate environment, you would know why it's offensive. General rule of thumb is, don't say it if you wouldn't say it to your mother. I certainly wouldn't say that to my mother.

Edit: to elaborate, corporations aren't concerned with being labeled as sexist. They are worried about being sued because of sexism, because it's one of the toughest kinds of corporate lawsuits to defend against, and one of the most lucrative kinds of lawsuits for the plaintiff. (IANAL though)