I find parasites offensive as well. Many definitions of parasite specifically cite people as the object being described. http://dictionary.reference.com/browse

I find parasites offensive as well. Many definitions of parasite specifically cite people as the object being described. http://dictionary.reference.com/browse/parasite http://dictionary.reference.com/browse/parasite a person who receives support, advantage, or the like, from another or others without giving any useful or proper return, as one who lives on the hospitality of others. (in ancient Greece) a person who received free meals in return for amusing or impudent conversation, flattering remarks, etc. Perhaps you are right as the definition of parasite in regards to people generally indicates living off others by their consent. Rather than living off others by threat or use of force.