Such a broad definition of anarchist means that there is space for lots of people in the big dis-harmonious tent, and that, at our best, we have room to all disagree with everyone else in that tent while reecognizing that disagreeing doesn't mean kicking them out of said tent. These disagreements help us to find people we feel true affinity for, as opposed to people with whom we band together based on a political doctrine imposed externally, or to match the stated ideology of a specific group.
For myself, my perspectives and analysis have changed in the time I have identified as an anarchist, and I hope they will continue to. The moment they stop is when my anarchism stops being anarchic. Which is not to say consistency isn't important, but that consistency should be adaptive.
What is bad about the broadness? almost the exact same thing. Lots of people use the label anarchist who are really not interested in eliminating the state, capitalism, and other forms of domination. Lots of people use the broadness of the label to further their own political ends. I have seen situations where no one wanted to act to remove individuals toxic to a particular group based upon everyone being anarchists, and us all trying to respect a diversity of perspectives. This isn't even beginning to get in to folks co-opting the label anarchist such as nationalist anarchists and anarcho-capitalists.