As I understand it the insight of labelling theory is that if you label someone as something then it prompts future behaviour in line with the label. It’s the reason, for example, why the justice system is sensitive about prematurely labelling young people as criminals. Young people who are labelled as criminals become criminals, whereas young people who are categorised as needing social support are less likely to become criminals. Labels are powerful.
In this sense I think JW use of labels is pretty dumb actually. They prematurely label people who have doubts and questions as “apostate” ironically ensuring that they do in fact become “apostate”. This may have worked during a period of growth when they could afford to lose large numbers of members, but as decline sets in I think it’s a policy that will increasingly backfire.