"It feels like he belongs to us." And everyone joined together in applause again.
Maybe you can tell your son that what they said made you feel sad and that you feel like they are trying to make him distant from you.
If he starts spouting JW propaganda about you needing to return to the bOrg, remind him that JWs have always championed everyone’s right to freedom of religion and then ask him if he thought it would be hypocritical to condemn or persecute someone for choosing a religion different from the watchtower. Ask him if it would be wrong for a Catholic's family to shun him if he were to covert to being a JW... then make the comparison in reverse with a JW becoming a [Insert Religion Name].
Make sure you use the word “persecute” in reference to how JWs treat you for using your freedom of religion. “Persecute” is a term JWs are used to only being used in reference to themselves and not anyone else. Using the term in a new context could jog his brain a bit and help him start to think on his own.
Remember, NEVER NEVER NEVER directly attack the WTS…. ALWAYS depict yourself as being persecuted for your religions beliefs. Doing this both disarms a JW and prevents the "aposto-shields" from coming up and also helps them to start thinking on their own.