The MatPat video failed to use any of the new knowledge gained from the grimoire that came from TTK, especially the Book of Sorrows. His information is outdated and the idea of an evil Traveler has been around for a while now. Reading the Book of Sorrows, it's pretty clear that the Traveler is running from Oryx and his siblings, as they seek to consume it's light. This doesn't mean that the Traveler is inherently good. There's still a bunch of mystery surrounding the Traveler's motives, but it's clear now that the Traveler isn't inherently evil.