The article states: "Though it still must be authenticated, it is likely a copy of an earlier document produced by a second-century Gnostic sect called the Cainites."
Notice, it is at best 2nd century. Historians normally give more weight to eye-witness accounts than those written long after the events. But, not so in the case of liberal Christian revisionists.
In the 4 gospels we have:
Matthew, an eye-witness
Mark, the "secretary" to Peter, an eye-witness
Luke, a contemporary of the apostles
John, an eye-witness
Yeah, the 2nd century documents should be given more weight..right.
Much of the Roman history is from sources that came several centuries later. Plutarch, Suetonius, etc. Polybius also to some extent.