I read the original article (9 pages long) in The New Republic Online. The Confederate flag issue was probably the most controversial thing in the article, as the MSM will beat it to death.
To me, the next most controversial part of the article revolves around a book that his younger sister has written about the family. Without going into detail, she wrote some pretty uncomplimentary things about Allen.
The things his sister said might be untrue or exaggerated...but if they are true, Allen is a sociopath who does not belong in any public office. Unfortunately, those are just the types of people who are drawn to seek political office, and DC already has an overabundance of them.