If you want to criticize how french people name that thing, you can remind them that when they want to refer to a "salle de bain", they will not only often use the english words "water closet", but they will also shorten it to "V-C". Yes. They pronounce it "VC". Not "WC". There are weird people in France.
(Note that the letter "W" is called "double v" in french, as opposed to "double u" in english.). Also note that it doesn't exist in Canada. That's a French thing.