Hello Victor_E:
Yes, any adult without a handful of literature would certainly be suspect. Also, any woman with a skirt cut above the knee or wearing any but the most modest top.
Certain jewelry, like a cross, is a definite no no. Also, anyone with a college ring would be under close observation, I suppose.
Even if an attendee is identified as an opposer, what can the security do if the person is not actively being disruptive? The assembly is defined as a public event, is it not? The rental contract likely states so. As we all know, the WTBTS has no problem lying whenever its suits them to do so, but I think they will hesitate in those cases when an unfavorable legal response is probable.
Just as the security persons work in teams, so should any opposers. If for nothing else, then they will have a witness as well should the matter go to court.
Ray Franz was written that he does not support anyone causing a disruption and for the most part I agree. But I see nothing wrong in trying to peaceably make the real truth available in a public venue, and if some JWs feel that they've been "disrupted", then that's their problem, not mine.