Start with the origin of the term "neocon." Decades ago, what we now know as the "liberal agenda" was written by people openly seeking to destroy America. A lot of people saw what they thought of as great ideas FOR America and embraced pretty-much the entire public liberal agenda as their own. They wanted a strong, independent liberal America. The founding liberals said destruction of America was so central to their ideology that agreeing with EVERYTHING ELSE but not hating America meant you might as well call yourself a conservative and thus the term "neoconservative" was born.
So there you have it. The difference is the neocons don't hate America.