The scribes and Pharisees had reputations for giving up on certain segments of their society. People were labeled as sinners, tax collectors, Samaritans, adulterers and lepers. They were the "unclean," unwelcome in worship, unwelcome among those who saw their position with God as secure. The labeling was a convenient way of dismissing others and absolving themselves from any responsibility of caring for them.
We shudder to think how people could do such a thing, but we see it still today. We, too, label people -- think of the possibilities! -- and thereby dismiss them, often subjecting them to social ostracism, not even willing to listen -- and thus, perhaps, to take a chance on learning something!
We cast them out. We discard them. We consider them so much trash.