In an unusually public spat, two prominent professors are trying to destroy one another’s careers amid charges of shoddy scholarship, anti-Semitism, and plagiarism. Alan Dershowitz and Norman Finkelstein have been at each other’s throats for years, but their battle was taken to a new level this year, when Dershowitz, who teaches at Harvard, began actively advocating against Mr. Finkelstein receiving tenure at DePaul University.