David Schwimmer has made a fascinating, gut-wrenching film about the insidious plague that has invaded the internet; disguised, depraved predators seducing unblemished children, whose false sense of maturity belies their age. “Trust” tackles 21st century issues where boundaries have dissolved: children, because of unlimited access to the internet, “chat rooms” where masquerade is legitimate, have lost the virginal purity of …