Plagiarism is intellectual theft.
It is illegal. Perpetrators can be prosecuted. Plagiarism is also unethical and just plain loathsome in all work, but especially so in sociology papers. Trust is a form of social capital that communities use to accomplish their goals. As Francis Fukuyama reminds us, Trust is the expectation that arises within a community of regular, honest, and cooperative behavior, based on commonly shared norms, on the part of other members of that community.