I don't like labeling people or labeling myself, but I know that we all unconsciously do it anyway. In my real life, some people are astounded when they hear about something I do (or know how to do) or think because they thought they knew everything about me. This is not usually about religion/belief in God, but it is an example about labeling and putting someone in a box.
I agree that this happens. It's unfortunate, but, as you said, we all do it.
I try very hard not to, though I'm sure I fail, too. But when someone else corrects me, I'm glad to learn their own views.