The practice of "shunning" of former employees of Jews for Jesus is described at http://www.exjewsforjesus.org/j4jquestions/shun.html
Another description of shunning is at http://www.exjewsforjesus.org/j4jquestions/#abusive which says that JFJ shunning included "various levels of cutting off communication with these former members, which have ranged from a complete prohibition against communicating with the person to less extreme forms of cut-off. Often rumors were spread about former members to damage their reputation."
Remember that these are former employees of an organization, not members of a church, that are being shunned, and that current employees are doing the "shunning." This shunning is talked about in some of the ex-Jews for Jesus stories. See, for example, http://www.exjewsforjesus.org/stories/mimi.html and also http://www.exjewsforjesus.org/stories/journey4.html
Apparently this unfortunate practice continues. If JFJ is disturbed by accusations that it is a cult, it should discontinue shunning, which is (sociologically speaking) one of the hallmark traits of a cult.