I like your take on the parasite idea. It would basically make anyone that is incapable of taking care of them self a parasite. could be the old or mentally ummm not normal. It could even get pushed as far as anyone that receives help to survive is a parasite. be it paied by govement or help from family and friends. Sounds like we could even say sorry i locked you in the cage and you need me to give you water or you will die so your a parasite and i can kill you now.
xD