I'd argue that you should very much care about the political alignment of extremist leaders, because it show you where an ideology can ultimately lead to if left unchecked. As the poster above said, it doesn't mean that all right-wing people are nazis, but knowing the nazis were right-wing shows you where a right-wing government can end up if the wrong set of conditions happen to come along. This is important information, as you can spot the warning signs as they appear and (hopefully) nip it in the bud before it gets to that point.