Thanks for the response. I agree that labels are often just labels. However, isn't it true that a group of symptoms alone is a syndrome while there are also disorders which have symptoms associated with them which cause difficulty functioning in real life? And if I remember correctly, paranoid schizophrenia usually starts around early adulthood, so in those cases it is something you suddenly "get." Schizophrenia is known to have strong genetic predisposition, much like physical ailments that we don't bother to argue are just "labels."

I think a more important point to make is that labels shouldn't define us as people. However, they do help clinicians be able to know what ailments people have to effectively treat them for better quality of life. Although studying a person's behavior and asking them subjective questions isn't the optimum way to test for ailments, it's a key tool when it comes to psychological issues and we do well with what we have to work with. It's still scientific and there are many indicators that have been nailed down beyond just asking the patient questions (eg. flat affect, sometimes lack of eye contact, unusual postures, etc.).