According to the Guardian Bishops who have expressed concern over comings have received death threats threatening them with death if they do not keep out of politics.
It would be interesting to hear the National Secular society response to this.
Since the NSS is a rational, law-abiding organisation, then that behaviour would be condemned. However, the Bishops themselves deserve strong censure for thinking they had any particularly valuable opinion on the matter and even if they had, as ordinary citizens, an opinion to express, they should not have done so under their Bishop title.