Ecumenism is 'in' at the moment; I mean ecumenism of the kind that seeks to bring Protestants and Catholics together with the aim of finding unity together, either through the means of joint evangelistic efforts or through dialogues thrashing out our differences til we all come to a common denominator. The Lutheran and Catholic joint declaration on justification is an example of such dialogue. At first glance it looks hope-giving, yet after further reflection you'll notice that words like 'grace' and 'faith' are largely undefined leaving one with the impression that the 'unity' fostered by the document is built on slippery terms.
Yet, is justification the only thing that Protestants should be concerned about in ecumenical dialogue? Mark Noll has even written a book arguing that the the reformation is now redundant! Wow! I didn't realise that Rome had repented of the blasphemy committed every Sunday at the mass, and of Marian devotion, and of the Papacy, and of the enforced celibacy of ministers and of the rampant pederasty among the clergy and of....oh wait, they haven't repented - DOH!
So in the light of these serious doctrinal and ecclesiastical concerns, the un-PC question one must ask is: is cooperation in the evangelistic sphere wise? For instance, would the apostles have held joint evangelistic rallies(!) with the 'angel worshippers' of Colossae and then entrust new converts to those who, through such practises, had been 'cut of from Christ' (Col 2:19)?