I think MM it comes down to how the person sees themselves, and whether they are secure in their self concept. If someone declares themself a christian, and follows their idea of what a christian is, who has the right to tell them they are not a real christian. When these beliefs remain a personal matter, and harm no-one else, why should we argue that they are not who they believe themselves to be.
There is a big difference between a label that someone applies to themselves, and a label that others try to force upon them.
For a person that knows who they are, and is secure in that knowledge, labeling from others does no damage psychologically. For a person that is insecure in who they are, such as children and vunerable adults, labeling can lead to a great deal of psychological damage. In these cases it is a form of abuse.
I do know that I am not an anti-christian, so when I get labeled as such by people on this forums, I can see it for what it is, an attempt to bait, much like kids in a playground calling someone names in an attempt to get a bite from the kid they're labeling.