The documentary is startlingly slanted, and almost every fact in it has been disputed (with evidence) somewhere or other. For example, on the topic of Piraha religion, and other parts of the story told in this documentary (like why the researcher Everett has been barred entry to the Piraha villages), you might view the interview here: http://www.youtube.com/watch?v=J3jWI4cPRMg. On whether Piraha has recursion or not, and whether the Chomskyans have actually been "hostile", or simply brought forward counterevidence, you can read the exchange that starts here: http://ling.auf.net/lingbuzz/000411 (with links to reply and counterreply). More recently, independent researchers have done work on the language and cast the "no recursion" claim into doubt:
http://www.nature.com/news/war-of-words-over-tribal-tongue-1.10595
http://ling.auf.net/lingbuzz/001095
http://www.letras.puc-rio.br/pag_profs/documentos/cilene/artigos/AbstractPirahaRodrigues&Sandalo.pdf
Hope this is helpful to you.
