The problem with time travel for historical research of such debated things is the same as the problem with uncomfortable facts for the masses today. No matter what you find, people, in general, won't change and all you can end up doing is starting a war. Then there are all those historical inaccuracies that we see today and no one corrects or cares about. On a personal level, it might be nice, on a society level, it's a death sentance.