So this is jw/WTS "security" people...they have no legal grounds to search anyone's belongings in the US.
That will definitely keep away non-jws with no family jw connections. They evidently don't want the "public" to be made welcome. Of course, it is easy to duplicate those badges. This is the so-called official reason to wear badges.
*** km 4/12 p. 5 par. 6 Our District Conventions—Powerful Testimony to the Truth ***
When we wear our convention badge, this not only serves to advertise the convention and enable other delegates to identify us but also gives a witness to onlookers. People in the convention city will observe that those wearing a convention badge are dressed neatly and modestly, not with the unkempt and provocative styles common in the world.
It's too bad you can't find a BOE letter to that effect, otherwise it could just be the over officious words of some self-important elders.
The attendants at the hall were told not to touch a belligerent person at the hall unless they were physically attacked and it was best to call the proper police.
*** km 12/89 p. 7 Question Box ***
In areas where security is a problem, attendants should be assigned to protect against vandalism or disturbances by opposers. If someone inside the Kingdom Hall tries to disrupt the meeting, he should be asked to leave. If he refuses and persists in causing a disturbance, the elders may contact the authorities. (Elders have additional written direction that will be helpful to them in such a situation.) In some areas it may be necessary for assigned brothers to check the Kingdom Hall parking area during meetings.—km 11/84 p. 4.