The New Zealand variant of this involved Glen Campbell asking any JWs present at his NZ concerts to stand up and then ordering them to leave. This was doing the rounds of JW gossip mills in the 1970s. Even at the time I kept hearing this, I wondered why I never actually net a Witness to whom this had happened - and the media never reported it. Then I heard John Denver had done this in the States.
Let's face it: it is a flimsy accusation and would immediately have caused a public outcry - NZ has long been an advocate of human rights, and if any visiting "superstar" had ever discriminated against a named religious group, members of the audience would have protested at the blatant discrimination.