I don’t believe you can square the use of parasite with a concern for that entity’s agency. It’s like trying to trust a person who says, “I don’t hate Jews because of their genetics; I call them rats because of the choices they’ve made.” Even if I grant that you don’t condemn people for being unproductive through no fault of their own, this parasite rhetoric still evokes imagery of hate toward desperate victims (like drug addicts and the mentally ill). It’s not like the people you’re calling parasites are benefiting from their behavior. They need rehabilitation and community more than condemnation.