Invalid Invalids

So this morning I overhead my mother scolding my younger sister about not wearing her seatbelt. She was saying something along the lines of " I don't really feel like caring for an invalid for the rest of my life. If you get in an accident, that's what'll happen." because of this, I've been chewing on the word "invalid" (pronounced In-vuh-lid as opposed to in-vAl-id) all day. Such an odd word. With a simple change of syllable emphasis it changes from a word that connotates insufficience to describing one who is unable to perform some sort of bodily function or is bedridden. I can see the connection, but I don't understand why people would even bother pronouncing it differently. A simple change in pronunciation doesn't mask the fact that it's a term that defines a human being as less than valid. It doesn't particularly offend me, but who do they think they're fooling? If you're really concerned about not offending people, use a word that isn't homonymous with invalid(In-vAl-id).