What should one say (if anything) to people in Crown Heights carrying something on Shabbos R”L because of the “Eiruv”?
This is not something unique to Crown Heights. This applies to any community where an Eiruv is rumored to have been erected, but it is done without consultation and support of the local Rabbonim, nor with any endorsement of any recognized Posek.
The response to your question depends on the nature of the person you are meeting. Something should be said and must be said but only if it’s a person that we may assume he or she will accept what is being said or at least will give it some thought. It would also be advisable to refrain from saying anything until they’ve arrived home and are no longer carrying something.
ראה במחשבות בעצה טז – בדומה לזה (בענינו). וראה שש״כ יז הערה קלט.
ויש לצרף עוד כמה צירופים בדיני תוכחה כשלא ישמעו, ותלוי בב׳ השיטות בשו״ע אדה״ז קנו, תרח, סדר הכנסת שבת. ודו״ק כי קיצרתי. והאריכות אך למותר. ואדרבה.