Leaving off the "saint" is not the most worrisome attack on the Christian aspect of this holiday. This is: http://www.vday.org/main.html.
Right now, at my "conservative" southern, state-run university, the campus is plastered with flyers for "The V----a Monologues," sponsored by the university's center for women's studies... Try explaining to your kid why they can't go see this play or what a v----a is.... Tasteless, tactless and just plain gross.
What is wrong with that?
I've never seen the Vagina Monologues and have no plan to. But you seem to think there's something inherently wrong with the word itself and/or explaining what it is to a child.
Better you should explain it than one of his/her school chums.