Why have we declared war on foreign dramatists?

On The Guardian Theatre blog, Guild member John Morrison accuses British theatre of abusing the work of playwrights not working in English.

One can argue that in the theatre anything goes, particularly when the author is safely dead and long out of copyright. But one of the principles that marks off theatre from film is respect for the artistic integrity of the author's text, even when he or she is no longer around to complain. That's why we squirm to think of Nahum Tate reworking King Lear in the 1680s to give Shakespeare's tragedy a happy ending.

Treating foreign works in this cavalier fashion sends the same message as the decline of language teaching in schools; we are increasingly a monoglot culture, treating classic plays in other languages as mere raw material for our own theatre.