I think labeling is something people should only do when their thinking who they themselves are. I mean, it's not important to label others and sometimes/often it's even rude, but it can help you understand your own sexuality and persona if you label yourself. You don't have to talk about that label to anyone though.
"Nobody ever asked what my orientation was when I was younger, people assumed that I was straight and nobody ever talked about it at school or at home." This for example is the same kind of labeling I've encountered in past which it caused some needless drama in my life when some people were "shocked" about my sexuality only because they had made assumptions in their heads.
It's natural that people have preconceptions about others, but it's important to acknowledge them and different them from facts so that you don't for example lip off something and end up hurting others. I always try to stay open-minded and not to categorize anyone before I get to know them as they are.