There’s something profoundly human about the scapegoat. From the ancient Israelites and Greeks to the Aztecs, global cultures have long sought to concentrate society’s ills in a single vessel, cleansing the rest of us in the process.Today, the Democratic foreign-policy establishment is looking for a scapegoat of its own. Tainted by the sins of enabling Israeli conduct in Gaza and beyond, many national-security mandarins are seeking absolution by…