Bootstrapping like HN would be ideal, since the users knew each other (YC startup founders) and set the tone for an ideal interaction. I'm not sure if there's a completely analogous gathering for film.
Furthermore, the communities for film appreciation and film making may behave differently on a film news website. While people who appreciate film can candidly talk about films, people who make films have vested stakes. This can make Filmmakers self-censor their thoughts. (e.g. They don't want to openly criticize a veteran filmmaker, since the veterans might have influence in the younger filmmaker's future production.)
Furthermore, the communities for film appreciation and film making may behave differently on a film news website. While people who appreciate film can candidly talk about films, people who make films have vested stakes. This can make Filmmakers self-censor their thoughts. (e.g. They don't want to openly criticize a veteran filmmaker, since the veterans might have influence in the younger filmmaker's future production.)