Muggles' Guide to Harry Potter/Magic/Blood traitor

Overview
A Blood traitor is a Pure Blood wizard who sympathizes with Muggle causes or with Muggles in general.

Extended Description
The term "Blood Traitor," a very emotionally loaded term, is first heard from the mad, screaming portrait of Mrs. Black in Number 12, Grimmauld Place. The insult is apparently leveled by Mrs. Black, a fanatical believer in the tenets of Blood status, at the Weasley family. We learn later that any family member who appears to consort with Muggles or Muggle-born wizards, or who sympathizes with them, is literally burned off the tapestry showing the family tree, as a display of their being eliminated from the family history.

Analysis
To those Wizards who accept the flawed belief structure known as Blood Status, Muggles are subhuman creatures who are beneath contempt. Thus, any Wizard who consorts with them, or who even sympathizes with them, is a traitor to Blood Status and to the purity of their own bloodline. A classic example of a Blood Traitor is Arthur Weasley, who despite springing from the oldest, purest Wizarding bloodlines, not only is amused by Muggles, but has been involved in drafting legislation aimed at protecting them from Wizards.