Here is an extreme example to prove this. I can say that I am a chair, and I can argue this until I'm blue in the face, but that won't change the fact that others will think that I am a human, not a chair. More relevant to the conversation, let's say I am a man that only has relationships with other men. I can call myself straight all I want, but if I tell other people about my behavior, they will categorize that behavior by the behavior(homosexual), thus it will not always align with the categorization that I apply to myself(straight). Okay or not, it is human nature to behave this way.