The fact that so many of the writers in this thread no longer use words perceived as offensive to some is evidence that in general we are moving towards a more sensitive, caring society. There seems to be greater awareness that words hurt. Once one has that awareness, Rossignol's wise directive: "Always remember - think before you speak" can be applied. Some groups, some populations, do not yet have that awareness. They get more aware if we all respond to their misuse of language and call them out on it. I imagine I will lose my attempt to get the word "douche" out of the lingo; however, when my students use that word, I inform them that it refers to a female sanitary device. They generally have no idea and don't want to imagine it. I'm not entirely sure if calling someone a douche or douchebag means they are useless and lazy or they are an evil, amoral scumbag. Either way, it sounds like a negative message being sent about vaginas. (Is it?)
I always interpreted it as a good thing (pro-vag if you will). Douching is a misguided and horrible thing for vaginas and calling someone a douche means that they're so horrible and toxic that they shouldn't be anywhere near a vagina.
That is the first, and only explanation for the etymlogy of the insult douche bag that I ever need to read. Perfect summation IMO.
How about proposing 'enema bag' as a substitute? It is more apt because insults are for sending negative messages about assholes, not vaginas. (Firefox's spellchecker assures me that the plural of 'vagina' is 'vaginae', but I don't believe it.)